Sheet for cell and cell device

ABSTRACT

A battery packet ( 50 ) comprises a battery case ( 51 ) formed by processing a battery case forming laminated sheet ( 10 ), a battery  50   a  contained in the battery case ( 51 ), and tabs ( 59, 60 ) extending outside from the battery case ( 51 ). The battery case forming laminated sheet ( 10 ) is formed by laminating a first base film layer ( 1   a ), i.e., an outermost layer, a metal foil layer ( 2 ), and a heat-adhesive resin layer ( 3 ) in that order. The first base film layer ( 1   a ) is a biaxially oriented polyethylene terephthalate resin film or a biaxially oriented nylon resin film. The metal foil layer ( 2 ) is an aluminum or copper foil. The heat-adhesive resin layer ( 3 ) is formed of a polyolefin resin, more preferably, of an acid-denatured polyolefin resin.

TECHNICAL FIELD

The present invention relates to a battery packet, and a battery caseforming sheet for forming a battery case for containing the componentelements of a battery.

BACKGROUND ART

Most conventional battery cases for containing the component elements ofa battery are metal cases. Various electronic apparatuses includingnotebook computers and portable telephone sets have been developed andhave diffused, and efforts have been made in recent years to reduce theweight and thickness of such electronic apparatuses. Demand for thedevelopment of lightweight, thin batteries requiring less space hasincreased with the progressive reduction in the weight and thickness ofsuch electronic apparatuses.

To meet such a demand, activities have been made for the research anddevelopment of various lightweight, thin sheet batteries usingelectrodes and electrolytes of polymeric materials. Nevertheless, anylight, thin battery cases for sheet batteries, satisfying all requisiteproperties including strength, moisture- and gas-impermeability, sealingperformance and adhesion to electrodes and terminals have not beenprovided.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the foregoing problemsand it is therefore an object of the present invention to provide alight, thin sheet for lightweight, thin battery cases, having excellentproperties in strength, durability, moisture and gas impermeability,sealing and adhesion to electrodes and terminals, and capable of beingeasily processed, and to provide a battery packet.

The present invention provides a battery case forming laminated sheetfor forming a battery case comprising a first base film, and aheat-adhesive resin layer formed on the inner side of the first basefilm,

a battery packet comprising a battery, a battery case containing thebattery, and tabs connected to the battery and projecting outside fromthe battery case, and

a battery packet comprising a battery, tabs connected to the battery,and a battery case containing the battery and the tabs, in which aperipheral part of the battery case is sealed, and recesses are formedin parts of the sealed peripheral part corresponding to the tabs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 5 are typical sectional views of a first embodiment accordingto the present invention;

FIGS. 6 to 9 are typical sectional views of a second embodimentaccording to the present invention;

FIGS. 10 to 12 are typical sectional views of a third embodimentaccording to the present invention;

FIGS. 13 to 16 are typical sectional views of a fourth embodimentaccording to the present invention;

FIGS. 17 to 20 are typical sectional views of a fifth embodimentaccording to the present invention;

FIGS. 21 to 23 are typical sectional views of a sixth embodimentaccording to the present invention;

FIGS. 24 to 28 are typical views of a seventh embodiment according tothe present invention;

FIGS. 29 to 33 are typical views of an eighth embodiment according tothe present invention;

FIGS. 34 to 36 are typical views of a ninth embodiment according to thepresent invention;

FIGS. 37 to 44 are typical views of a tenth embodiment according to thepresent invention;

FIGS. 45 to 48 are typical views of an eleventh embodiment according tothe present invention;

FIGS. 49 to 54 are typical views of a twelfth embodiment according tothe present invention;

FIGS. 55 to 57 are typical views of a thirteenth embodiment according tothe present invention;

FIGS. 58 to 60 are typical views of a fourteenth embodiment according tothe present invention;

FIGS. 61 to 64 are typical views of a fifteenth embodiment according tothe present invention;

FIGS. 65 to 69 are typical views of a sixteenth embodiment according tothe present invention;

FIGS. 70 and 71 are typical views of a seventeenth embodiment accordingto the present invention;

FIGS. 72 to 73 are typical views of an eighteenth embodiment accordingto the present invention;

FIGS. 74 and 75 are typical views of a nineteenth embodiment accordingto the present invention;

FIGS. 76 and 77 are typical views of a twentieth embodiment according tothe present invention; and

FIG. 78 is a typical views of a twenty-first embodiment according to thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

A first embodiment according to the present invention will be describedwith reference to FIGS. 1 to 5. A polymer battery packet 50 will bedescribed with reference to FIG. 5.

The polymer battery packet 50 comprises a battery case 51, a polymerbattery 50 a contained in the battery case 51, and a pair of tabs 59 and60 connected to the polymer battery 50 a and projecting outside from thebattery case 51.

The battery case 51 is formed by heat-sealing laminated sheets, whichwill be described later.

The polymer battery 50 a has an electrolytic gel layer 53 containing anorganic electrolyte, a positive terminal 55 overlying the electrolyticgel layer 53, a negative terminal 56 underlying the electrolytic gellayer 53, and collectors 57 and 58 connected to the positive terminal 55and the negative terminal 56, respectively. The collector 57 connectedto the positive terminal 55 is made of Al, and the collector 58connected to the negative terminal 56 is made of Cu.

The tab 59 connected to the positive terminal 55 is a metal tab of Al ora stainless steel, and the tab 60 connected to the negative terminal 56is a metal tab of Cu, Ni or a stainless steel.

A separator 54 formed by cutting a porous film is embedded in theelectrolytic gel layer 53 containing an organic electrolyte. Theseparator 54 is not necessarily be embedded in the electrolytic gellayer 53.

The polymer battery 50 a may be of a coiled construction, a laminatedconstruction or a folded construction.

The polymer battery 50 a may be a lithium polymer battery. Components ofa lithium ion polymer battery (LIP) and a lithium metal polymer battery(LP) are tabulated below.

TABLE Lithium polymer battery LIP battery LP battery Positive terminalLi-containing metal Vanadium ox- oxide (Co, Ni, Mn ide/polymer oxide)Negative terminal Carbon Metallic lithium Collector Metal foil, meshedmetal sheet, punched metal sheet, knitted carbon fiber fabricElectrolyte Electrolytic gel containing organic electrolyte SeparatorReinforcing porous films, nonwoven fabrics Thickness of sepa- 70 to 200μm rator Internal structure Wound, laminated or folded

In the polymer battery packet 50 shown in FIG. 5, a potential differenceis created between the tabs 59 and 60 extending from the polymer battery50 a, and electric energy can be derived through the tabs 59 and 60.

The battery case 51 will be described. The battery case 51 is formed byheat-sealing laminated sheets (battery case forming sheets).

Any one of laminated sheets described in the following paragraphs (1) to(4) is used for forming the battery case 51. In the laminated sheets (1)to (4), each of first second and third base film is a biaxially orientedpolyethylene terephthalate film (hereinafter referred to as “PET film”)or a biaxially oriented nylon film (hereinafter referred to as “ONfilm”).

(1) First base film layer/Metal foil layer/Heat-adhesive resin layer

(2) First base film layer/Second base film layer/Metal foil layer/Heatadhesive resin layer

(3) First base film layer/Metal foil layer/Third base filmlayer/Heat-adhesive resin layer

(4) First base film layer/Second base film layer/Metal foil layer/Thirdbase film layer/Heat-adhesive resin layer

These battery case forming sheets are superposed with the heat-adhesiveresin layers in contact with each other, side edge parts and end edgeparts of the sheets are bonded together by heat-sealing to form abattery case 51 having the shape of a pouch having one open end, thecomponents of the battery 50 a including the positive terminal 55, thenegative terminal 56 and the electrolytic gel layer 53 are put in thebattery case 51, the tabs 59 and 60 are extended outside the batterycase 51, and the heat-adhesive resin layers of the edge parts of thesheets of the open end, and the heat-adhesive resin layers of the edgeparts of the sheets and the tabs 59 and 60 are bonded together byheat-sealing.

The heat-adhesive resin layers of the sheets are formed of aheat-adhesive resin adhesive not only to itself, but also to the tabs 59and 60 formed of a conductive material, such as a copper foil or analuminum foil.

The metal foil layer sandwiched between the base film layers or betweenthe base film layer and the heat-adhesive resin layer serves as aexcellent barrier to moisture and gases, and is protected by the first,the second and/or the third base film layer and/or the heat-adhesiveresin layer. Therefore, the metal foil layer will not be fissured andany pinholes will not be formed in the metal foil layer, so that themetal foil layer is able to maintain its satisfactory gas-impermeableproperty.

The first, the second or the third base film layer laminated to theouter or the inner surface of the metal foil layer protects the metalfoil layer, gives strength and resistance to various hazardous externaleffects to the sheet, and the heat-adhesive resin layer, i.e., theinnermost layer, gives a heat-sealable property to the sheet.

At least the first base film layer is formed on one surface of the metalfoil layer, and at least the heat-adhesive resin layer is formed on theother surface of the metal foil layer. Since the first base film layerand the heat-adhesive resin layer are electrically nonconductive, thebattery case forming sheet is an electrically nonconductive sheet.

The heat-adhesive resin layer of the laminated sheet is anacid-denatured polyolefin resin having an acid content in the range of0.01 to 10% by weight.

The acid-natured polyolefin resin forming the heat-adhesive resin layeris satisfactorily heat-adhesive not only to itself, but also to the tabs59 and 60 of copper or aluminum. Therefore, the battery case resemblinga pouch having one open end can easily be formed by heat-sealing, andthe open end through which the tabs 59 and 60 of a metal foil, such as acopper or aluminum foil, extend can satisfactorily and hermetically besealed by heat-sealing after placing the components of the battery inthe battery case.

Materials of the battery case forming sheet according to the presentinvention and methods of processing the materials will be describedhereinafter.

The battery case forming sheet according to the present invention has,as an intermediate layer, the metal foil layer highly impermeable tomoisture and gases, some of the first, the second and the third basefilm layer are laminated to one or both the surfaces of the metal foillayer, and the heat-adhesive resin layer is formed as the innermostlayer.

An aluminum foil and a copper foil are suitable materials for formingthe gas-impermeable metal foil layer, i.e., the intermediate layer. Analuminum foil is the most preferable material for forming the metal foillayer because an aluminum foil is inexpensive, easy to process and easyto bond to a film. A suitable thickness of the metal foil layer is inthe range of 5 to 25 μm.

Each of the first, the second and the third base film layer may be, forexample, a PET film, an ON film, a polyethylene naphthalate film, apolyimide film or a polycarbonate film. PET films and ON films areparticularly suitable in view of durability, ability, processability andeconomy.

Although there is no significant difference in properties between PETfilms and ON films, PET films have a low hygroscopic property and areexcellent in rigidity, abrasion resistance and heat resistance, and ONfilms have a relatively high hygroscopic property and are excellent inflexibility, piercing strength, bending strength and low-temperatureresistance.

The thicknesses of those base films are in the range of 5 to 100 μm,more preferably, in the range of 12 to 30 μm.

As mentioned above, it is preferable that the heat-adhesive resin layer,i.e., the innermost layer, is satisfactorily heat-adhesive not only toitself, but also to the metal forming the tabs 59 and 60, and have a lowhygroscopic property and a low moisture adsorptivity to restrict theleakage of moisture into the electrolyte of the polymer battery 50 a tothe least possible extent. It is also preferable that the heat-adhesiveresin layer is stable and unsusceptible to the swelling and corrosiveactions of the electrolyte.

Heat-adhesive resins meeting such requirements are, for example,ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers,ethylene-methacrylate copolymers, and polyolefin resins prepared byblending a polyethylene resin and one or some of the foregoingcopolymers, and polyolefin resins prepared by blending a polypropyleneresin and one or some of the foregoing copolymers. Particularlypreferable heat-adhesive resins are acid-denatured polyolefin resinsproduced by modifying ethylene-acrylic acid copolymers,ethylene-methacrylic acid copolymers, polyethylene resins, polypropyleneresins, and resins produced by graft copolymerization includingethylene-propylene copolymers, ethylene-α-olefin copolymers,propylene-α-olefin copolymers, ethylene-vinyl acetate copolymers,ethylene-acrylate copolymers, ethylene-methacrylate copolymers andterpolymers of those resins by some of unsaturated carboxylic acids andunhydrides of unsaturated carboxylic acides, such as acrylic acid,methacrylic acid, maleic acid, maleic anhydride, citraconic anhydride,itaconic acid and itaconic anhydride.

Ionomers produced by cross-linking the resins having carboxyl groupsincluded in those resins by Na⁺ ions or Zn²⁺ ions are suitable materialsfor forming the heat-adhesive resin layer.

Preferable acid content of the acid-denatured polyolefin resins is inthe range of 0.01 to 10% by weight. The heat-adhesion of the resin to ametal is insufficient if the acid content is less than 0.01% by weight,and the film forming performance of the resin is inferior if the acidcontent is higher than 10% by weight.

A suitable thickness of the heat-adhesive resin layer is in the range of10 to 100 μm.

The component layers may be laminated by a known dry lamination methodusing a two-component polyurethane adhesive or an extrusion laminationmethod (also called a sandwich lamination method) which extrudes amolten heat-adhesive resin, such as a polyethylene resin, between twofilms and compresses the layers of the films and a layer of theheat-adhesive resin sandwiched between the films.

The innermost heat-adhesive resin layer may be formed by attaching aheat-adhesive resin film to a film by a dry lamination method or anextrusion lamination method. If necessary, a molten heat-adhesive resinmay be applied to a surface of a film coated with an anchor coatingmaterial (AC material, i.e., a primer) by extrusion coating.

The present invention will more concretely be described with referenceto the accompanying drawings.

FIGS. 1, 2, 3 and 4 are typical sectional views of battery case formingsheets in examples in accordance with the present invention for formingthe battery case 51.

Referring to FIG. 1, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a metal foil layer2 and a heat-adhesive resin layer 3. The first base film layer 1 a is aPET film or an ON film serving as the outermost layer. The metal foillayer 2 is, for example, an aluminum foil. Preferably, the heat-adhesiveresin layer 3 is a layer of an acid-denatured polyolefin resin having anacid content in the range of 0.01 to 10% by weight.

The first base film layer 1 a, such as a PET film or an ON film, formingthe outermost layer of the battery case forming sheet 10 provides thebattery case forming sheet 10 with various kinds of mechanical strengthincluding tensile strength, piercing strength and bending strength, andvarious kinds of resistance including abrasion resistance, waterresistance, chemical resistance, heat resistance and low-temperatureresistance. The metal foil layer, such as an aluminum foil layer, i.e.,an intermediate layer, serves as a barrier layer impermeable to moistureand gases. The heat-adhesive resin layer, i.e., the innermost layer, isa layer of an acid-denatured polyolefin resin having an acid content inthe range of 0.01 to 10% by weight and provides the battery case formingsheet 10 with excellent heat-sealable property.

If the metal foil layer is a 9 μm thick aluminum foil, the metal foillayer has a water vapor permeability of 0.01 g/m²·24 hr or below at 40°C. and 90% RH. The water vapor impermeability can easily be enhanced.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/Acid-denatured polyolefin resin layer (40 μm thick)

{circle around (2)} ON film (15 μm thick)/Aluminum foil (9 μmthick)/Acid-denatured polyolefin resin layer (40 μm thick)

Referring to FIG. 2, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a second base film1 b, a metal foil layer 2 and a heat-adhesive resin layer 3. The firstbase film layer 1 a is the outermost layer.

The battery case forming sheet 10, as compared with the sheet 10 shownin FIG. 1, is provided additionally with the second base film 1 b toimprove the ability of the first base film 1 a on the outer side of themetal foil layer 2, and a two-layer base film is formed by the firstbase film layer 1 a and the second base film layer 1 b.

Each of the first base film layer 1 a and the second base film layer 1 bis a PET film or an ON film.

Although the first base film layer 1 a and the second base film layer 1b may be the same types of films, it is preferable to use differenttypes of films, such as a PET film and an ON film as the first base filmlayer 1 a and the second base film layer 1 b, respectively, in view ofmakinging the respective properties of the first base film layer 1 a andthe second base film layer 1 b complement each other.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/ON film (15 μmthick)/Aluminum foil (9 μm Fun thick)/Acid-denatured polyolefin resinlayer (40 μm thick)

{circle around (2)} ON film (15 μm thick)/PET film (12 μmthick)/Aluminum foil (9 μm thick)/Acid-denatured polyolefin resin layer(40 μm thick)

Referring to FIG. 3, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a metal foil layer2, a third base film 1 c and a heat-adhesive resin layer 3. The firstbase film layer 1 a is the outermost layer.

The battery case forming sheet 10, as compared with the battery caseforming sheet 10 shown in FIG. 1, is provided additionally with thethird base film 1 c sandwiched between the intermediate metal foil layer2 and the heat-adhesive resin layer 3 to provided the sheet 10 withstabler barrier effect by enhancing metal foil layer protecting effect.

Each of the first base film layer 1 a and the third base film layer 1 cis a PET film or an ON film.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Acid-denatured polyolefin resin layer (40μm thick)

{circle around (2)} PET film (12 μm thick)/Aluminum foil (9 μm thick)/ONfilm (15 μm thick)/Acid-denatured polyolefin resin layer (40 μm thick)

{circle around (3)} ON film (15 μm thick)/Aluminum foil (9 μm thick)/PETfilm (12 μm thick)/Acid-denatured polyolefin resin layer (40 μm thick)

{circle around (4)} ON film (15 μm thick)/Aluminum foil (9 μm thick)/ONfilm (15 μm thick)/Acid-denatured polyolefin resin layer (40 μm thick)

The battery case forming sheet 10, as compared with the battery caseforming sheet 10 shown in FIG. 1, is provided additionally with thethird base film 1 c to provide the sheet 10 with improved various kindsof mechanical strength and resistance to detrimental effects. Since themetal foil layer 2 is sandwiched between the first base film layer 1 aand the third base film layer 1 c, the metal foil layer 2 is protectedmore effectively from both external and internal shocks, abrasion,physical actions and chemical actions, and the sheet 10 has a furtherstable barrier effect.

Referring to FIG. 4, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a second base filmlayer 1 b, a metal foil layer 2, a third base film 1 c and aheat-adhesive resin layer 3. The first base film layer 1 a is theoutermost layer.

The battery case forming sheet 10, as compared with the battery caseforming sheet 10 shown in FIG. 2, is provided additionally with thethird base film 1 c sandwiched between the metal foil layer 2 and theheat-adhesive resin layer 3.

The first, second and third base film layers 1 a, 1 b and 1 c providesthe sheet 10 with improved various kinds of mechanical strength andresistance to detrimental effects. Since the metal foil layer 2 issandwiched between the laminated layer of the first base film layer 1 aand the second base film layer 1 b, and the third base film layer 1 c,the metal foil layer 2 is further effectively protected for the stablerbarrier effect.

When printing a picture of letters and patterns on the surface of eachof the battery case forming sheets 10 shown in FIGS. 1 to 4, the pictureis printed on the inner surface of the first base film layer to bebonded to the surface of the adjacent layer for second-surfacedecoration, and then the first base film layer is laminated to theadjacent layer. The thus printed picture will not be damaged even if thesurface of the sheet 10 is abraded.

As is apparent form the foregoing description, the present inventionprovides lightweight, thin, flexible, battery case forming sheetsexcellent in various kinds of mechanical strength, resistance todetrimental effects, impermeability to moisture and gases,heat-sealability and processability, and capable of being efficientlyproduced.

Second Embodiment

A second embodiment according to the present invention will be describedwith reference to FIGS. 6 to 9. A battery case forming sheet in thesecond embodiment is any one of the following laminated sheets (1) to(4). The laminated sheets in the second embodiment are substantially thesame in construction as those in the first embodiment, except that thelaminated sheets in the second embodiment have a laminated heat-adhesiveresin layer consisting of a polyolefin resin layer and an acid-denaturedpolyolefin resin layer.

(1) First base film layer/Metal foil layer/Heat-adhesive resin layer

(2) First base film layer/Second base film layer/Metal foillayer/Heat-adhesive resin layer

(3) First base film layer/Metal foil layer/Third base filmlayer/Heat-adhesive resin layer

(4) First base film layer/Second base film layer/Metal foil layer/Thirdbase film layer/Heat-adhesive resin layer

The innermost heat-adhesive resin layer is formed by laminating apolyolefin resin layer and an acid-denatured polyolefin resin layerhaving an acid content in the range of 0.01 to 10% by weight, and theheat-adhesive resin layer is laminated to the adjacent layer so that theacid-denatured polyolefin resin layer forms the innermost surface. Sincethe acid-denatured polyolefin resin layer is heat-adhesive not only toitself, but also to metals, such as copper and aluminum, a battery caseformed by processing the battery case forming sheet and having the shapeof a pouch having one open end through which the tabs 59 and 60 extendoutside from the battery case can be sealed by satisfactorilyheat-sealing the open end of the battery case.

Since both the polyolefin resin layer and the acid-denatured polyolefinresin act as heat-adhesive resin layers, the heat-sealed part of thebattery case has a sufficient adhesive strength. The hygroscopicproperty and the moisture adsorbing property of the acid-denaturedpolyolefin resin are relatively high as compared with those ofpolyolefin resins, such as polyethylene and polypropylene, and hence theacid-denatured polyolefin resin tends to contain moisture. However,since the acid-denatured polyolefin resin layer of the heat-adhesiveresin layer can be formed in a small thickness, the moisture content ofthe heat-adhesive resin layer can be restricted to the least possibleextent and the effect of moisture contained in the heat-adhesive resinlayer on the electrolyte can be prevented.

Since at least the first base film layer and the heat-adhesive resinlayer are attached to the opposite sides of the metal foil layer,respectively, and both the first base film layer and the heat-adhesiveresin layer are electrically nonconductive, the battery case formingsheet serves as an electrically nonconductive sheet.

Each of the first, the second and the third base film layer of thelaminated sheet is a biaxially oriented polyethylene terephthalate film(hereinafter referred to as “PET film”) or a biaxially oriented nylonfilm (hereinafter referred to as “ON film”).

Since PET films and ON films are flexible, are excellent in strengthincluding tensile strength, bending strength and piercing strength,resistance including abrasion resistance, heat resistance,low-temperature resistance and chemical resistance, processability forlamination, and economy, the battery case forming sheet having excellentproperties can be produced at a high efficiency and at a low cost.

Materials of the battery case forming sheet according to the presentinvention and methods of processing the materials will be describedhereinafter.

The battery case forming sheet according to the present invention has,as an intermediate layer, the metal foil layer highly impermeable tomoisture and gases, one or some of the first, the second and the thirdbase film layer excellent in various kinds of strength and resistance todetrimental effects are laminated to one or both the surfaces of themetal foil layer, and the laminated heat-adhesive resin layer consistingof the polyolefin resin layer and the acid-denatured polyolefin resinlayer is formed as the innermost layer.

An aluminum foil and copper foil are suitable materials for forming thegas-impermeable metal foil layer, i.e., the intermediate layer. Analuminum foil is the most preferable material for forming the metal foillayer because an aluminum foil is inexpensive, easy to process and easyto bond to a film. A suitable thickness of the metal foil layer is inthe range of 5 to 25 μm.

The first, the second and the third base film layer may be layers of,for example, PET films, ON films, polyethylene naphthalate films,polyimide films and polycarbonate films. PET films and ON films areparticularly suitable in view of durability, ability, processability andeconomy.

Although there is no significant difference in properties between PETfilms and ON films, PET films have a low hygroscopic property and areexcellent in rigidity, tensile strength, abrasion resistance and heatresistance, and ON films have a relatively high hygroscopic property andare excellent in flexibility, piercing strength, bending strength andlow-temperature resistance.

The thicknesses of those base films are in the range of 5 to 100 μm,more preferably, in the range of 12 to 30 μm.

As mentioned above, it is preferably that the heat-adhesive resin layer,i.e., the innermost layer, is satisfactorily heat-adhesive not only toitself, but also to metal terminals, and have a low hygroscopic propertyand a low moisture adsorptivity to restrict the leakage of moisture intothe electrolyte of a polymer battery to the least possible extent. It isalso preferable that the heat-adhesive resin layer is stable andunsusceptible to the swelling and corrosive actions of the electrolyte.

To meet such requirements, the present invention uses a laminatedheat-adhesive resin layer consisting of a polyolefin resin layer and anacid-denatured polyolefin resin layer having an acid content in therange of 0.01 to 10% by weight.

The acid-denatured polyolefin resin layer is formed in the leastnecessary thickness and is laminated to the polyolefin resin layer so asto form the innermost layer in order that the heat-adhesive resin layercan satisfactorily be heat-bonded to terminals formed by processing ametal foil and to restrict the moisture content of the heat-adhesiveresin layer to the least possible extent.

Polyolefin resins suitable for forming the polyolefin resin layer of theheat-adhesive resin layer meeting such requirements are, for example,polyethylene resins, polypropylene resins, ethylene-propylenecopolymers, ethylene-α-olefin copolymers, ethylene-vinyl acetatecopolymers, ethylene-acrylate copolymers, ethylene-methacrylatecopolymers, terpolymers of those resins, and resins prepared by blendingsome of those resins.

Suitable resins for forming the acid-denatured polyolefin resin layerhaving an acid content in the range of 0.01 to 10% by weight of theheat-adhesive resin layer are, for example, resins produced by modifyingethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers,polyethylene resins, polypropylene resins, and resins produced by graftcopolymerization including ethylene-propylene copolymers,ethylene-α-olefin copolymers, propylene-α-olefin copolymers,ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers,ethylene-methacrylate copolymers and terpolymers of those resins by someof unsaturated carboxylic acids and unhydrides of unsaturated carboxylicacides, such as acrylic acid, methacrylic acid, maleic acid, maleicanhydride, citraconic anhydride, itaconic acid and itaconic anhydride.The resin having an acid content in the range of 0.01 to 10% by weightis excellent in heat-adhesion to metals.

Ionomers produced by cross-linking the resins having carboxyl groupsincluded in those resins by Na⁺ ions or Zn²⁺ ions are suitable materialsfor forming the heat-adhesive resin layer.

Preferable acid content of the acid-denatured polyolefin resins is inthe range of 0.01 to 10% by weight. The heat-adhesion of the resin to ametal is insufficient if the acid content is less than 0.01% by weight,and the film forming performance of the resin is inferior if the acidcontent is higher than 10% by weight.

The acid-denatured polyolefin resin has high heat-adhesion to metals,whereas the same has a relatively high hygroscopic property and arelatively high moisture adsorbing property.

Accordingly, the present invention uses the heat-adhesive resin layer ofa laminated sheet consisting of the polyolefin resin layer and theacid-denatured polyolefin resin layer to make the most of the advantagesof the acid-denatured polyolefin resin and to make the polyolefin resinlayer and the acid-denatured polyolefin resin layer complement eachother, forms the innermost layer of the sheet by a acid-denaturedpolyolefin resin layer of the least possible thickness to suppress theinfluence of moisture to the least extent.

A suitable thickness of the heat-adhesive resin layer is in the range of10 to 100 μm, and the thickness of the acid-denatured polyolefin resinlayer is in the range of 1 to 50 μm, more preferably, in the range of 5to 25 μm.

The battery case forming sheet in accordance with the present inventioncan be formed by properly laminating some of the first, the second andthe third base film layer, the metal foil layer, and the heat-adhesiveresin layer formed by laminating the polyolefin resin and theacid-denatured polyolefin resin layer. The first to the third base filmlayers and the metal foil layer are laminated by a known dry laminationmethod using, for example, a two-component polyurethane adhesive or byan extrusion lamination method which extrudes a molten heat-adhesiveresin, such as a polyethylene resin, between two films and compressesthe layers of the films and a layer of the heat-adhesive resinsandwiched between the films.

The heat-adhesive resin layer can be formed by putting together apolyolefin resin film of a predetermined thickness and an acid-denaturedpolyolefin resin film of a predetermined thickness formed by amultilayer tubular film extrusion method and laminating the polyolefinresin film and the acid-denatured polyolefin resin film by a drylamination method or an extrusion lamination method. The heat-adhesiveresin layer can be formed also by coating a surface of a base sheetformed by properly laminating some of the first to the third base filmlayers and the metal foil layer with an anchor coating material (ACmaterial, i.e., a primer), and laminating a polyolefin resin layer of apredetermined thickness and an acid-denatured polyolefin resin layer ofa predetermined thickness to the surface of the base sheet coated withthe anchor coating material by coextrusion using a coextrusion machine.

Examples of the second embodiment will concretely be describedhereinafter with reference to the drawings.

Examples shown in the drawings are illustrative and not limitative. Likeor corresponding parts are designated by the same reference charactersthroughout the drawings.

FIGS. 6 to 9 are typical sectional views of examples of battery caseforming sheets in accordance with the present invention.

Referring to FIG. 6, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a metal foil layer2 and a heat-adhesive resin layer 3 consisting of a polyolefin resinlayer 3 a and an acid-denatured polyolefin resin layer 3 b. The firstbase film layer 1 a is the outermost layer.

Preferably, the first base film layer 1 a is a PET film or an ON film.Preferably, the metal foil layer 2 is, for example, an aluminum foil.The acid-denatured polyolefin resin layer 3 b of the heat-adhesive resinlayer 3 is a layer of an acid-denatured polyolefin resin having an acidcontent in the range of 0.01 to 10% by weight.

The first base film layer 1 a, such as a PET film or an ON film, formingthe outermost layer of the battery case forming sheet 10 provides thebattery case forming sheet 10 with various kinds of mechanical strengthincluding tensile strength, piercing strength and bending strength, andvarious kinds of resistance including abrasion resistance, waterresistance, chemical resistance, heat resistance and low-temperatureresistance. The metal foil layer 2, such as an aluminum foil layer,i.e., an intermediate layer, serves as a barrier layer impermeable tomoisture and gases. As mentioned above, the polyolefin resin layer 3 aand the acid-denatured polyolefin resin layer 3 b having an acid contentin the range of 0.01 to 10% by weight of the heat-adhesive resin layer 3provide the battery case forming sheet 10 with excellent heat-sealableproperty and have a low moisture content.

If the metal foil layer is a 9 μm thick aluminum foil, the metal foillayer has a water vapor permeability of 0.01 g/m²·24 hr or below at 40°C. and 90% RH. The water vapor impermeability can easily be enhanced.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/Polyethylene layer (30 μm thick)/Acid-denatured polyolefin resinlayer (10 μm thick)

{circle around (2)} ON film (15 μm thick)/Aluminum foil (9 μmthick)/Polyethylene layer (30 μm thick)/Acid-denatured polyolefin resinlayer (10 μm thick)

Referring to FIG. 7, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a second base film1 b, a metal foil layer 2 and a heat-adhesive resin layer 3 consistingof a polyolefin resin layer 3 a and an acid-denatured polyolefin resinlayer 3 b. The first base film layer 1 a is the outermost layer.

The battery case forming sheet 10, as compared with the sheet 10 shownin FIG. 6, is provided additionally with the second base film 1 b toimprove the ability of the first base film 1 a on the outer side of themetal foil layer 2, and a two-layer base film is formed by the firstbase film layer 1 a and the second base film layer 1 b.

Each of the first base film layer 1 a and the second base film layer 1 bis a PET film or an ON film.

Although the first base film layer 1 a and the second base film layer 1b may be the same types of films, it is preferable to use differenttypes of films, such as a PET film and an ON film as the first base filmlayer 1 a and the second base film layer 1 b, respectively, in view ofmaking the respective properties of the first base film layer la and thesecond base film layer 1 b complement each other.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/ON film (15 μmthick)/Aluminum foil (9 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

{circle around (2)} ON film (15 μm thick)/PET film (12 μmthick)/Aluminum foil (9 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

The base film layers of the battery case forming sheet 10 of thisconstruction on the outer side of the aluminum foil layer have both theadvantages of the PET film and the ON film in addition to the effects ofthe battery case forming sheet 10 shown in FIG. 6. Thus, the outersurface of the battery case forming sheet 10 has enhanced various kindsof mechanical strength and resistance, and has generally excellentproperties.

Referring to FIG. 8, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a metal foil layer2, a third base film 1 c and a heat-adhesive resin layer 3 consisting ofa polyolefin resin layer 3 a and an acid-denatured polyolefin resinlayer 3 b. The first base film layer 1 a is the outermost layer.

The battery case forming sheet 10, as compared with the battery caseforming sheet 10 shown in FIG. 6, is provided additionally with thethird base film 1 c sandwiched between the intermediate metal foil layer2 and the heat-adhesive resin layer 3 (directly, the polyolefin resinlayer 3 a) to provided the sheet 10 with stabler barrier effect byenhancing the effect of protecting the metal foil layer 2 by sandwichingthe metal foil layer 2 between the first base film layer 1 a and thethird base film layer 1 c.

Each of the first base film layer 1 a and the third base film layer 1 cis a PET film or an ON film.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

{circle around (2)} PET film (12 μm thick)/Aluminum foil (9 μm thick)/ONfilm (15 μm thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

{circle around (3)} ON film (15 μm thick)/Aluminum foil (9 μm thick)/PETfilm (12 μm thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

{circle around (4)} ON film (15 μm thick)/Aluminum foil (9 μm thick)/ONfilm (15 μm thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

The battery case forming sheet 10, as compared with the battery caseforming sheet 10 shown in FIG. 6, is provided additionally with thethird base film 1 c to provide the sheet 10 with improved various kindsof mechanical strength and resistance to detrimental effects. Since themetal foil layer 2 is sandwiched between the first base film layer 1 aand the third base film layer 1 c, the metal foil layer 2 is protectedmore effectively from both external and internal shocks, abrasion,physical actions and chemical actions, and the sheet 10 has a stablerbarrier effect.

Referring to FIG. 9, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a second base filmlayer 1 b, a metal foil layer 2, a third base film 1 c and aheat-adhesive resin layer 3 consisting of a polyolefin resin layer 3 aand an acid-denatured polyolefin resin layer 3 b. The first base filmlayer 1 a is the outermost layer.

The battery case forming sheet 10, as compared with the battery caseforming sheet 10 shown in FIG. 7, is provided additionally with thethird base film 1 c sandwiched between the metal foil layer 2 and theheat-adhesive resin layer 3 (directly, the polyolefin resin layer 3 a).

Therefore, as shown in FIG. 9, the first base film layer 1 a and thesecond base film layer 1 b are laminated to the outer surface of themetal foil layer 2, and the third base film layer 1 c is sandwichedbetween the metal foil layer 2 and the heat-adhesive resin layer 3.

The battery case forming sheet 10 additionally provided with the thirdbase film layer 1 c has, in addition to the functions and effects of thebattery case forming sheet 10 shown in FIG. 7, improved various kinds ofmechanical strength and resistance to detrimental effects. Since themetal film layer 2 is sandwiched between the laminated layer of thefirst base film layer 1 a and the second base film layer 1 b, and thethird base film layer 1 c, the metal foil layer 2 is further effectivelyprotected for the stabler barrier effect.

When printing a picture of letters and patterns on the surface of eachof the battery case forming sheets 10 shown in FIGS. 6 to 9, the pictureis printed on the inner surface of the first base film layer 1 a to bebonded to the surface of the adjacent layer for second-surfacedecoration, and then the first base film layer is laminated to theadjacent layer. The thus printed picture will not be damaged even if thesurface of the sheet 10 is abraded.

As is apparent form the foregoing description, the present inventionprovides lightweight, thin, flexible, battery case forming sheetsexcellent in various kinds of mechanical strength, resistance todetrimental effects, impermeability to moisture and gases,heat-sealability and processability, and capable of being efficientlyproduced.

Third Embodiment

A third embodiment according to the present invention will be describedwith reference to FIGS. 10 to 12. A battery case forming sheet in thethird embodiment is any one of the following laminated sheets (1) to(3). The battery case forming sheet in the third embodiment issubstantially the same as the battery case forming sheet in the firstembodiment, except that, in the laminated sheets in the thirdembodiment, each of a first base film layer and a second base film layeris a biaxially oriented polyethylene terephthalate film (hereinafterreferred to as “PET film”) coated with a silicon dioxide thin film, analuminum oxide thin film or a polyvinylidene chloride film thin, abiaxially oriented nylon film (hereinafter referred to as “ON film”)coated with a silicon dioxide thin film, an aluminum oxide thin film ora polyvinylidene chloride thin film, or a biaxially orientedpolypropylene film (hereinafter referred to as “OPP film”) coated with asilicon dioxide thin film, an aluminum oxide thin film or apolyvinylidene chloride thin film, and a heat-adhesive resin layer is asingle-layer structure of an acid-denatured polyolefin resin layer or atwo-layer laminated sheet of a polyolefin resin layer and anacid-denatured polyolefin resin layer.

(1) First base film layer/Heat-adhesive resin layer

(2) First base film layer/Second base film layer/Heat-adhesive resinlayer

(3) First base film layer/Saponified ethylene-vinyl acetate copolymerlayer/Second base film layer/Heat-adhesive resin layer

In the battery case forming sheet of the laminated sheet (1), the firstbase film layer is formed by coating a surface of a PET film, an ON filmor an OPP film with a thin film of silicon dioxide, aluminum oxide or apolyvinylidene chloride. The PET film, the ON film or the OPP filmprovides the sheet with various kinds of strength including tensilestrength, bending strength and piercing strength, and various kinds ofresistance including abrasion resistance, heat resistance,low-temperature resistance and chemical resistance, and the thin film ofsilicon dioxide, aluminum oxide or a polyvinylidene chloride coating thesurface of the PET, ON or OPP film serves as a barrier layer impermeableto moisture and gases.

A PET film, as compared with an ON film, has a relatively lowhygroscopic property and is excellent in rigidity, tensile strength,abrasion resistance and heat resistance. An ON film, as compared with aPET film, has a somewhat high hygroscopic property and is excellent inflexibility, piercing strength, bending strength and low-temperatureresistance. An OPP film has a particularly low hygroscopic property andexcellent moisture-proof property, high tensile strength and highrigidity.

The heat-adhesive resin layer is a single-layer structure of anacid-denatured polyolefin resin layer or a two-layer laminated sheet ofa polyolefin resin layer and an acid-denatured polyolefin resin layer.If the heat-adhesive resin layer of a two-layer structure is used, thepolyolefin resin layer is on the side of the first base film layer, andthe acid-denatured polyolefin resin layer serves as the innermost layerof the battery case forming sheet. In either case, the acid-denaturedpolyolefin resin layer is the innermost layer. Since the acid-denaturedpolyolefin resin layer is heat-adhesive not only to itself, but also tometals, such as copper and aluminum, a battery case formed by processingthe battery case forming sheet and having the shape of a pouch havingone open end through which the tabs 59 and 60 extend outside from thebattery case can be sealed by satisfactorily heat-sealing the open endof the battery case.

The hygroscopic property and the moisture adsorbing property of theacid-denatured polyolefin resin forming the innermost layer of thebattery case forming sheet are relatively high as compared with those ofpolyolefin resins, such as polyethylene and polypropylene, and hence theacid-denatured polyolefin resin may possibly absorb moisture containedin the atmosphere. Such a hygroscopic property of the acid-denaturedpolyolefin resin is detrimental to the electrolyte.

However, since the acid-denatured polyolefin resin layer of theheat-adhesive resin layer can be formed in a small thickness when theacid-denatured polyolefin resin layer is used in combination with thepolyolefin resin layer, the amount of moisture, if any, contained in theheat-adhesive resin layer is only a little. Therefore, the effect ofmoisture can be restricted to the least extent and satisfactoryheat-adhesive property can be maintained.

The battery case forming sheet of the laminated sheet (2) has a basefilm layer of a two-layer structure consisting of the first base filmlayer and the second base film layer. The base film layer can be, forexample, a combination of a PET film and an ON film, which enables themost use of the respective characteristics of the PET film and the ONfilm in addition to effects of the battery case forming sheet of thelaminated sheet (1). The first and the second base film layer provideenhanced mechanical strength and resistance to detrimental effects. Thebattery case forming sheet has the two thin films coating the first andthe second base film layer, i.e., the thin film of silicon dioxide film,the thin film of aluminum oxide and/or the thin film of polyvinylidenechloride, and even if one of the two thin films is broken, the other canserve as a barrier to moisture and gases. Thus, the battery case formingsheet has enhanced impermeability to moisture and gases.

The battery case forming sheet of the laminated sheet (3) is formed byadditionally inserting a saponified ethylene-vinyl acetate copolymerbetween the first and the second base film layer of the battery caseforming sheet of the laminated sheet (2). The battery case forming sheetof the laminated sheet (3) has a further enhanced and stabilizedimpermeability to moisture and gases.

The battery case forming sheet of the laminated sheet (3) having thethree barrier layers impermeable to moisture and gases has, in additionto the effects of the battery case forming sheet of the laminated sheet(2), a high, stable permeability to moisture and gases.

As mentioned above, the battery case forming sheet in accordance withthe present invention does not use a conductive metal foil, such as analuminum foil, as a barrier layer, and all the component layers of thesheet are made of electrically nonconductive materials. Therefore,accidental short-circuiting will not occur even if the tabs 59 and 60extended outside the battery case 51 are bent, which ensures highsafety.

The acid-denatured polyolefin resin forming the acid-denaturedpolyolefin resin layer has an acid content in the range of 0.01 to 10%by weight.

The acid-denatured polyolefin resin layer is easy to form and isheat-adhesive not only to itself, but also to metals, such as copper andaluminum. Accordingly, a battery case formed by processing the batterycase forming sheet and having the shape of a pouch having one open endthrough which the tabs 59 and 60 extend outside from the battery casecan be sealed by satisfactorily heat-sealing the open end of the batterycase.

Materials of the battery case forming sheet according to the presentinvention and methods of processing the materials will be describedhereinafter.

Each of the first base film layer and the second base film layer is aPET film, an ON film or an OPP film having a surface coated with asilicon dioxide thin film, an aluminum oxide thin film or apolyvinylidene chloride thin film serving as a gas-impermeable barrierlayer.

The thin film of silicon dioxide or aluminum oxide may be formed over asurface of a PET film an ON film or an OPP film by a vacuum evaporationmethod or a sputtering method. When necessary, the surface of the PETfilm, the ON film or the OPP film may be coated with a known primercoating before forming the thin film of silicon dioxide or the aluminumoxide.

The thickness of the thin film layer of silicon dioxide or aluminumoxide is in the range of 150 to 2000 Å, more preferably, in the range of300 to 800 Å.

The polyvinylidene chloride thin film can be formed by a known coatingmethod on a PET or On film serving as a base film layer. A suitablethickness of the polyvinylidene chloride thin film is in the range of 1to 10 μm.

A saponified ethylene-vinyl acetate copolymer film may be used as agas-impermeable barrier layer. The saponified ethylene-vinyl acetatecopolymer film may be formed on the base film layer by a known drylamination method or an extrusion lamination method.

A suitable thickness of the saponified ethylene-vinyl acetate copolymerfilm is in the range of 10 to 40 μm.

As mentioned above, it is preferable that the heat-adhesive resin layerforming the innermost layer of the battery case forming sheet issatisfactorily heat-adhesive not only to itself, but also to a metalforming the terminals, has a low hygroscopic property and a low moistureadsorbing property to restrict the leakage of moisture into theelectrolyte to the least possible extent, and is stable and resistant tothe swelling and corrosive action of the electrolyte.

The heat-adhesive resin layer may be formed of an acid-denaturedpolyolefin resin. Suitable acid-denatured polyolefin resins are thoseproduced by modifying ethylene-acrylic acid copolymers,ethylene-methacrylic acid copolymers, polyethylene resins, polypropyleneresins, and resins produced by graft copolymerization includingethylene-propylene copolymers, ethylene-α-olefin copolymers,propylene-α-olefin copolymers, ethylene-vinyl acetate copolymers,ethylene-acrylate copolymers, ethylene-methacrylate copolymers andterpolymers of those resins by some of unsaturated carboxylic acids andunhydrides of unsaturated carboxylic acides, such as acrylic acid,methacrylic acid, maleic acid, maleic anhydride, citraconic anhydride,itaconic acid and itaconic anhydride.

Ionomers produced by cross-linking the resins having carboxyl groupsincluded in those resins by Na⁺ ions or Zn²⁺ ions are suitable materialsfor forming the heat-adhesive resin layer.

Preferable acid content of the acid-denatured polyolefin resins is inthe range of 0.01 to 10% by weight. The heat-adhesion of the resin to ametal is insufficient if the acid content is less than 0.01% by weight,and the film forming performance of the resin is inferior if the acidcontent is higher than 10% by weight.

The heat-adhesive resin layer may be a single-layer structure of one ofthe foregoing acid-denatured polyolefin resin or may be a two-layerlaminated sheet consisting of a polyolefin resin layer and a layer ofone of the foregoing acid-denatured polyolefin resins.

The heat-adhesive resin layer of a laminated sheet may consists of apolyolefin resin layer of a polyethylene resin, a polypropylene resin,an ethylene-propylene copolymer, an ethylene-α-olefin copolymer, anethylene-vinyl acetate copolymer, an ethylene-acrylate copolymer, anethylene-methacrylate copolymer, an ethylene-propylene copolymer or aterpolymer of some of those resins. These resins may be usedindividually or in a resin prepared by blending some of those resins.

A suitable thickness of the heat-adhesive resin layer is in the range of10 to 100 μm, and a suitable thickness of the acid-denatured polyolefinresin layer is in the range of 1 to 50 μm, more preferably, in the rangeof 5 to 25 μm.

The battery case forming sheet in accordance with the present inventionconsists of those layers, i.e., a desired combination of some of thefirst base film layer, the second base film layer, the saponifiedethylene-vinyl acetate copolymer layer, and the heat-adhesive resinlayer having the acid-denatured polyolefin resin layer or both thepolyolefin resin layer and the acid-denatured polyolefin resin layer.

These layers may be laminated by a known dry lamination method, a knownextrusion lamination method or an extrusion coating method.

When forming the laminated sheet (1), the first base film layer iscoated with an anchor coat (a primer coat), and then a layer of anacid-denatured polyolefin resin or layers of a polyolefin resin and anacid-denatured polyolefin resin may be formed by an extrusion method ora multilayer extrusion method on the first base film layer. Theheat-adhesive resin layer can be formed by putting together resin filmsof predetermined thicknesses formed by a tubular film extrusion methodby a dry lamination method using, for example, a two-componentpolyurethane adhesive or by extruding a polyethylene resin or otherheat-adhesive resin between resin layers and compressing the resinlayers.

The first and the second base film layer of the laminated sheet (2) canbe laminated by either a dry lamination method or an extrusionlamination method. The heat-adhesive resin layer can be formed by themethod employed in forming the heat-adhesive resin layer of thelaminated sheet (1).

The saponified ethylene-vinyl acetate copolymer layer can be formed byforming a saponified ethylene-vinyl acetate copolymer film in apredetermined thickness, and the first base film layer, the saponifiedethylene-vinyl acetate copolymer layer and the second base film layercan be laminated by either a dry lamination method or an extrusionlamination method. The heat-adhesive resin layer can be formed by themethod employed in forming the heat-adhesive resin layer of thelaminated sheet (1).

Examples of the third embodiment will concretely be describedhereinafter with reference to the drawings.

Examples shown in the drawings are illustrative and not limitative. Likeor corresponding parts are designated by the same reference charactersthroughout the drawings.

FIGS. 10 to 12 are typical sectional views of examples of battery caseforming sheets in accordance with the present invention.

A battery case forming sheet 10 shown in FIG. 10(a) is formed bylaminating a first base film layer 1 a, i.e., an outer layer, and anacid-denatured polyolefin resin layer, i.e., a heat-adhesive resin layer3.

The first base film layer 1 a is a PET film or an ON film having asurface coated with a silicon dioxide thin film, an aluminum oxide thinfilm or a polyvinylidene chloride thin film. Preferably, theheat-adhesive resin layer 3 is joined to the coated surface of the firstbase film layer 1 a to prevent damaging the silicon dioxide thin film,the aluminum oxide thin film or the polyvinylindene chloride thin filmcoating the first base film layer 1 a by abrasion or the like.

Preferably, the acid-denatured polyolefin resin layer 3 is formed of anacid-denatured polyolefin resin having an acid content in the range of0.01 to 10% by weight.

In this battery case forming sheet 10, the PET film, an ON film or anOPP film serving as the outermost first base film layer 1 a provides thesheet 10 with mechanical strength including tensile strength, piecingstrength and bending strength, and resistance including abrasionresistance, water resistance, chemical resistance, heat resistance andlow-temperature resistance. The silicon dioxide thin film, the aluminumoxide thin film or the polyvinylindene chloride thin film coating thefirst base film layer 1 a provides the sheet 10 with excellentimpermeability to moisture and gases. The heat-adhesive resin layer 3provides the sheet 10 with an excellent heat-sealability.

The acid-denatured polyolefin resin, as compared with an polyolefinresin, is relatively high in hygroscopic property and moisture adsorbingproperty. However, the amount of moisture contained in theacid-denatured polyolefin resin layer is small and any practical problemwill not arise when the battery cases formed by processing the sheet 10are not stored in a high-temperature high-humidity place for a longtime.

A battery case forming sheet 10 shown in FIG. 10(b) is formed bylaminating a first base film layer 1 a, i.e., an outer layer, and aheat-adhesive resin layer 3 consisting of a polyolefin resin layer 3 aand an acid-denatured polyolefin resin layer 3 b instead of theheat-adhesive resin layer 3 of the battery case forming sheet 10 shownin FIG. 10(a).

Although an anchor coat layer or a bonding layer of an adhesive for drylamination is formed between the first base film layer 1 a and theheat-adhesive resin layer 3 in each of the sheets 10 shown in FIGS.10(a) and 10(b), such an anchor coat layer or a bonding layer is asubsidiary element and hence is omitted in FIGS. 10, 11 and 12.

The acid-denatured polyolefin resin layer 3 b of the heat-adhesive resinlayer 3 of the battery case forming sheet 10 shown in FIG. 10(b) may beformed in a thickness smaller than that of the acid-denatured polyolefinresin layer serving as the heat-adhesive resin layer 3 of the sheet 10shown in FIG. 10(a). Therefore, the amount of moisture contained in theacid-denatured polyolefin resin layer 3 b is small even if theacid-denatured polyolefin resin layer 3 b absorbs moisture, and hencethe heat-adhesive layer 3 of the sheet 10 shown in FIG. 10(b) has a lowhygroscopic property.

The following are representative examples of the laminated sheets shownin FIGS. 10(a) and 10(b).

{circle around (1)} PET film (16 μm thick)/Silicon dioxide thin filmlayer (500 Å thick)/Acid-denatured polyolefin resin layer (40 μm thick)

{circle around (2)} PET film (16 μm thick)/Silicon dioxide thin filmlayer (500 Å thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

{circle around (3)} ON film (16 μm thick)/Polyvinylidene chloride filmlayer (3 μm thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

A battery case forming sheet 10 shown in FIG. 11(a) is formed by addinga second base film 1 b to the battery case forming sheet 10 shown inFIG. 10(a). The sheet 10 shown in FIG. 11(a) is formed by sequentiallylaminating a fist base film layer 1 a, the second base film layer 1 b,and a heat-adhesive resin layer 3 of an acid-denatured polyolefin resin.The first base film layer 1 a is the outermost layer.

Although the first base film layer 1 a and the second base film layer 1b may be the same types of films, it is preferable to use differenttypes of films, such as a PET film and an ON film as the first base filmlayer 1 a and the second base film layer 1 b, respectively, in view ofmaking the respective properties of the first base film layer 1 a andthe second base film layer 1 b complement each other. The battery caseforming sheet 10 shown in FIG. 11(a) has enhanced various kinds ofmechanical strength and resistance in addition to the effects of thebattery case forming sheet 10 shown in FIG. 10(a), and has an improvedimpermeability to moisture and gases because the sheet 10 is providedwith two barrier layers of silicon dioxide, aluminum oxide and/orpolyvinylidene chloride.

A battery case forming sheet 10 shown in FIG. 11(b) is similar inconstruction as the battery case forming sheet 10 shown in FIG. 11(a)and is provided with a heat-adhesive resin layer 3 consisting of apolyolefin resin layer 3 a and an acid-denatured polyolefin resin layer3 b instead of the heat-adhesive resin layer 3 of an acid-denaturedpolyolefin resin of the battery case forming sheet 10 shown in FIG.11(a).

The acid-denatured polyolefin resin layer 3 b of the heat-adhesive resinlayer 3 of the battery case forming sheet 10 shown in FIG. 11(b) may beformed in a small thickness. Therefore, the heat-adhesive layer 3 of thesheet 10 shown in FIG. 11(b) has a satisfactory heat-adhesive propertyand a low hygroscopic property.

The following are representative examples of the laminated sheets shownin FIGS. 11(a) and 11(b).

{circle around (1)} ON film (15 μm thick) with silicon dioxide thin filmlayer (500 Å thick)/PET film (12 μm thick) with silicon dioxide thinfilm layer (500 Å thick)/Acid-denatured polyolefin resin layer (40 μmthick)

{circle around (2)} PET film (12 μm thick) with silicon dioxide thinfilm layer (500 Å thick)/ON film (12 μm thick) with silicon dioxide thinfilm layer (500 Å thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

A battery case forming sheet 10 shown in FIG. 12(a) is formed byadditionally inserting a saponified ethylene-vinyl acetate copolymerlayer 9, i.e., a barrier layer, between the first base film layer 1 aand the second base film layer 1 b of the battery case forming sheet 10shown in FIG. 11(a); that is, the battery case forming sheet 10 shown inFIG. 12(a) is formed by sequentially laminating a first base film layer1 a, a saponified ethylene-vinyl acetate copolymer layer 9, a secondbase film layer 1 b, and a heat-adhesive resin layer 3 of anacid-denatured polyolefin resin.

The battery case forming sheet 10 thus provided with the three barrierlayers has an impermeability to moisture and gases higher than that ofthe battery case forming sheet 10 shown in FIG. 11(a).

A battery case forming sheet 10 shown in FIG. 12(b) is similar inconstruction as the battery case forming sheet 10 shown in FIG. 12(a)and is provided with a heat-adhesive resin layer 3 consisting of apolyolefin resin layer 3 a and an acid-denatured polyolefin resin layer3 b instead of the heat-adhesive resin layer 3 of an acid-denaturedpolyolefin resin of the battery case forming sheet 10 shown in FIG.12(a).

The battery case forming sheet 10 shown in FIG. 12(b) is formed bysequentially laminating a first base film layer 1 a, a saponifiedethylene-vinyl acetate copolymer layer 9, a second base film 1 b, apolyolefin resin layer 3 a and an acid-denatured polyolefin resin layer3 b. The first base film layer 1 a is the outermost layer.

The acid-denatured polyolefin resin layer 3 b of the heat-adhesive resinlayer 3 of the battery case forming sheet 10 shown in FIG. 12(b) may beformed in a small thickness. Therefore, the heat-adhesive layer 3 of thesheet 10 shown in FIG. 12(b) has a satisfactory heat-adhesive propertyand a low hygroscopic property, and the battery case forming sheet 10has the most excellent composite ability.

The followings are representative examples of the laminated sheets shownin FIGS. 12(a) and 12(b).

{circle around (1)} PET film (12 μm thick) with silicon dioxide thinfilm layer (500 Å thick)/Saponified ethylene-vinyl acetate copolymerlayer (25 μm thick)/PET film (12 μm thick) with silicon dioxide thinfilm layer (500 Å thick)/Acid-denatured polyolefin resin layer (40 μmthick)

{circle around (2)} PET film (12 μm thick) with silicon dioxide thinfilm layer (500 Å thick)/Saponified ethylene-vinyl acetate copolymerlayer (25 μm thick)/PET film (12 μm thick) with silicon dioxide thinfilm layer (500 Å thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

{circle around (3)} PET film (12 μm thick) with silicon dioxide thinfilm layer (500 Å thick)/Saponified ethylene-vinyl acetate copolymerlayer (25 μm thick)/ON film (15 μm thick) with silicon dioxide thin filmlayer (500 Å thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

When printing a picture of letters and patterns on the surface of eachof the battery case forming sheets 10 shown in FIGS. 10 to 12, thepicture is printed on the inner surface of the first base film layer tobe bonded to the surface of the adjacent layer for second-surfacedecoration, and then the first base film layer is laminated to theadjacent layer. The thus printed picture will not be damaged even if thesurface of the sheet 10 is abraded.

As is apparent from the foregoing description, the present inventionprovides lightweight, thin, flexible, battery case forming sheetsexcellent in various kinds of mechanical strength, resistance todetrimental effects, impermeability to moisture and gases,heat-sealability and processability; suitable for forming a battery casecapable of satisfactorily sealing the component parts of a batterytherein and of protecting the components of the battery from the adverseeffect of moisture, and excellent in securing safety in preventingshort-circuiting even if terminals of a conductive metal extendingoutside from the battery case are bent; and capable of being efficientlyproduced.

Fourth Embodiment

A fourth embodiment according to the present invention will be describedwith reference to FIGS. 13 to 16. A battery case forming sheet in thefourth embodiment is any one of the following laminated sheets (1) to(4), each of a first base film layer, a second base film layer and athird base film layer of the battery case forming sheet is a biaxiallyoriented polyethylene terephthalate film, a biaxially oriented nylonfilm or a biaxially oriented polypropylene film, and a heat-adhesiveresin layer of the battery case forming sheet is a single-layerstructure of an acid-denatured polyolefin resin layer or a two-layerlaminated sheet of a polyolefin resin layer and an acid-denaturedpolyolefin resin layer. The battery case forming sheet is provided witha metal foil layer smaller than the other layers, and having at leastone end edge lying on the inner side of the corresponding end edges ofthe other layers and not exposed at the edge of the battery case formingsheet. The battery case forming sheet in the fourth embodiment is thesame in other respects as that in the first embodiment.

(1) First base film layer/Metal foil layer/Heat-adhesive resin layer

(2) First base film layer/Second base film layer/Metal foil layer/Heatadhesive resin layer

(3) First base film layer/Metal foil layer/Second base filmlayer/Heat-adhesive resin layer

(4) First base film layer/Second base film layer/Metal foil layer/Thirdbase film layer/Heat-adhesive resin layer

The metal foil layer, i.e., an intermediate layer, of the battery caseforming sheet is smaller than the other layers, and at least one endedge thereof lies on the inner side of the end edges of the other layersand is not exposed at the edge of the battery case forming sheet. Thebattery case 51 having the open end part through which the tabs 59 and60 are extended outside the battery case 51 is formed by heat-sealingtwo battery case forming sheets in the fourth embodiment so that an endpart in which the end edge of the metal foil layer is on the inner sideof the edges of the other layers of each battery case forming sheetforms the open end part of the battery case 51. The size of the metalfoil layer is determined so that the end edge of the metal foil layerbarely reaches a heat-sealed part formed by heat-sealing the open end ofthe battery case 51. When the battery case 51 is thus formed, the tabs59 and 60 are not short-circuited by the battery case 51 even if thetabs 59 and 60 are bent, which improves the safety of the battery case51. The metal foil layer serves as an excellent barrier layerimpermeable to moisture and gases.

Since the metal foil layer is sandwiched between some of the first, thesecond and the third base film layer and the heat-adhesive resin layer,the metal foil layer is protected satisfactorily, fissures and pinholeswill not be formed in the metal foil layer, and hence the excellentimpermeable property of the metal foil layer can be maintained.

Each of the first, the second and the third base film layer on theopposite sides of the metal foil layer is a biaxially orientedpolyethylene terephthalate film (hereinafter referred to as “PET film”),a biaxially oriented nylon film (hereinafter referred to as “ON film”)or a biaxially oriented polypropylene film (hereinafter referred to as“OPP film”). The first, the second and the third base film layer protectthe metal foil layer and provides the battery case forming sheet withstrength, functions and various kinds of resistance to detrimentaleffects.

The heat-adhesive resin layer, i.e., the innermost layer, is asingle-layer structure of an acid-denatured polyolefin resin layer or atwo-layer laminated sheet of a polyolefin resin layer and anacid-denatured polyolefin resin layer. The innermost layer of thebattery case forming sheet provided with the heat-adhesive resin layerof either the single-layer structure or the two-layer laminated sheet isthe acid-denatured polyolefin resin layer. The acid-denatured polyolefinresin layer is satisfactorily heat-adhesive not only to itself, but alsoto metals, such as copper and aluminum. Accordingly, a battery caseformed by processing the battery case forming sheet and having the shapeof a pouch having one open end through which the tabs 59 and 60 extendoutside from the battery case can be sealed by satisfactorilyheat-sealing the open end of the battery case.

Although the acid-denatured polyolefin resin forming the innermost layerof the battery case forming sheet is superior to polyolefin resins, suchas polyethylene resins and polypropylene resins, in heat-adhesion tometals, the acid-denatured polyolefin resin has relatively highhygroscopic property and moisture adsorbing property and, in some cases,may possibly absorb some moisture contained in the atmosphere.

Although the degree of moisture absorption of the acid-denaturedpolyolefin resin layer rarely cause practical problems, the presentinvention employs a heat-adhesive resin layer consisting of a polyolefinresin layer and an acid-denatured polyolefin resin layer and forms theacid-denatured polyolefin resin layer in a small thickness for theenhancement of the quality of the battery case forming sheet.

When such a heat-adhesive resin layer is employed, the amount ofmoisture, if any, contained in the heat-adhesive resin layer is only alittle. Therefore, the effect of moisture can be restricted to the leastextent and satisfactory heat-adhesive property can be maintained.

The acid content of the acid-denatured polyolefin resin layer of theheat-adhesive resin layer in the range of 0.01 to 10% by weight.

The acid-denatured polyolefin resin layer of such a property exhibitssatisfactory film forming performance, and is highly adhesive not onlyto itself, but also to metals, such as copper and aluminum. Accordingly,a battery case formed by processing the battery case forming sheet andhaving the shape of a pouch having one open end through which the tabs59 and 60 extend outside from the battery case can be sealed bysatisfactorily heat-sealing the open end of the battery case.

Materials of the battery case forming sheet according to the presentinvention and methods of processing the materials will be describedhereinafter.

As mentioned above, the battery case forming sheet in accordance withthe present invention employs, as an intermediate layer, a metal foillayer highly impermeable to moisture and gases, and is formed byproperly laminating one or some of the first, the second and the thirdbase film layer excellent in various kinds of strength and resistance tothe outer surface or the opposite surfaces of the metal foil layer andforming, as the innermost layer, the heat-adhesive resin layer of asingle-layer structure of an acid-denatured polyolefin resin layer or atwo-layer laminated sheet of a polyolefin resin layer and anacid-denatured polyolefin resin layer so that at least one end edge ofthe metal foil layer lies on the inner side of the corresponding endedges of the other layers and is not exposed at the edge of the batterycase forming sheet.

An aluminum foil and a copper foil are suitable materials for formingthe gas-impermeable metal foil layer, i.e., the intermediate layer. Analuminum foil is the most preferable material for forming the metal foillayer because an aluminum foil is inexpensive, easy to process and easyto bond to a film. A suitable thickness of the metal foil layer is inthe range of 5 to 25 μm.

The first, the second and the third base film layers may be, forexample, a PET film, an ON film, an OPP film, a polyethylene naphthalatefilm, a polyimide film or a polycarbonate film. PET films and ON filmsand OPP films are particularly suitable in view of durability, ability,processability and economy.

Although there is no significant difference in properties between PETfilms and ON films, PET films have a low hygroscopic property and areexcellent in rigidity, abrasion resistance and heat resistance, and ONfilms have a relatively high hygroscopic property and are excellent inflexibility, piercing strength, bending strength and low-temperatureresistance.

The thicknesses of those base films are in the range of 5 to 100 μm,more preferably, in the range of 12 to 30 μm.

As mentioned above, it is preferable that the heat-adhesive resin layer,i.e., the innermost layer, is satisfactorily heat-adhesive not only toitself, but also to the metal forming the tabs 59 and 60, and have a lowhygroscopic property and a low moisture adsorptivity to restrict theleakage of moisture into the electrolyte to the least possible extent.It is also preferable that the heat-adhesive resin layer is stable andunsusceptible to the swelling and corrosive actions of the electrolyte.

To meet such requirements, the heat-adhesive resin layer is formed in asingle-layer structure of an acid-denatured polyolefin resin layer or atwo-layer laminated sheet of a polyolefin resin layer and anacid-denatured polyolefin resin layer.

Preferably, the acid content of an acid-denatured polyolefin resinforming the acid-denatured polyolefin resin layer is in the range of0.01 to 10% by weight.

Materials suitable for forming the polyolefin resin layer of theheat-adhesive resin layer are, for example, polyethylene resins,polypropylene resins, ethylene-propylene copolymers, ethylene-α-olefincopolymers, terpolymers of the foregoing polymers. These materials maybe used individually or in a resin prepared by blending some of thoseresins.

Resins suitable for forming the acid-denatured resin layer of theheat-adhesive resin layer are, for example, ethylene-acrylic acidcopolymers, ethylene-methacrylic acid copolymers, and resins produced bymodifying polyethylene resins, polypropylene resins, and resins producedby graft copolymerization including ethylene-propylene copolymers,ethylene-α-olefin copolymers, propylne-α-olefin copolymers,ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers,ethylene-methacrylate copolymers and terpolymers of those resins by someof unsaturated carboxylic acids and unhydrides of unsaturated carboxylicacides, such as acrylic acid, methacrylic acid, maleic acid, maleicanhydride, citraconic anhydride, itaconic acid and itaconic anhydride.

Ionomers produced by cross-linking the resins having carboxyl groupsincluded in those resins by Na⁺ ions or Zn²⁺ ions are suitable materialsfor forming the heat-adhesive resin layer.

Acid-denatured polyolefin resins having an acid content in the range of0.01 to 10% by weight are satisfactory in film forming performance and asatisfactorily heat-adhesive not only to itself, but also to metals.

The heat-adhesion of the resin to a metal is insufficient if the acidcontent is less than 0.01% by weight, and the film forming performanceof the resin is inferior if the acid content is higher than 10% byweight.

Although the acid-denatured polyolefin resins are highly heat-adhesiveto metals, the acid-denatured polyolefin resins have relatively highhygroscopic property and moisture adsorbing property.

Therefore, the present invention may use, instead of a heat-adhesiveresin layer of a single-layer structure of an acid-denatured polyolefinresin layer, a heat-adhesive resin layer of a two-layer laminated sheetconsisting of a polyolefin resin layer and an acid-denatured polyolefinresin layer serving as the innermost layer. The acid-denaturedpolyolefin resin layer is formed in the least possible thickness toreduce the effect of moisture to the least possible extent.

A suitable thickness of the heat-adhesive resin layer is in the range of10 to 100 μm. When the heat-adhesive resin layer is of a two-layerlaminated sheet, it is preferable that the thickness of theacid-denatured polyolefin resin layer is in the range of 1 to 50 μm,more preferably, in the range of 5 to 25 μm.

The battery case forming sheet in accordance with the present inventionis formed by properly laminating some of the first to the third basefilm layer, the metal foil layer and the heat-adhesive resin layer sothat at least one end edge of the metal foil layer, i.e., theintermediate layer, lies on the inner side of the end edges of the otherlayers.

When forming the laminated sheet, the first to the third base film layerand the metal foil layer may be laminated by a known dry laminationmethod using, for example, a two-component polyurethane adhesive or byan extrusion lamination method which extrudes a molten heat-adhesiveresin, such as a polyethylene resin, between two films and compressesthe layers of the films and a layer of the heat-adhesive resinsandwiched between the films.

A surface of the base film sheet may be coated with an anchor coatingmaterial (AC material, i.e., a primer coating) and then anacid-denatured polyolefin resin layer of a desired thickness, or apolyolefin resin layer of a desired thickness and an acid-denaturedpolyolefin resin layer of a desired thickness may be laminated to thesurface coated with the anchor coating material of the base film layerby an extrusion method or a multilayer extrusion method. Theheat-adhesive resin layer can be formed by putting together resin filmsof a predetermined thicknesses formed by a tubular film extrusion methodby a dry lamination method.

A battery case forming sheet having a metal foil layer not exposed inthe edges thereof can easily be manufactured by laminating a base filmserving as one of the first to the third base film layer, and a metalfoil so that the opposite end edges of the metal foil are 10 to 15 mm onthe inner side of the corresponding end edges of the base film, andtrimming the opposite end edge parts of the base film along lines 1 to 2mm on the outer side of the opposite end edges of the metal foil.

Examples of the fourth embodiment will concretely be describedhereinafter with reference to the drawings.

Examples shown in the drawings are illustrative and not limitative. Likeor corresponding parts are designated by the same reference charactersthroughout the drawings.

FIGS. 13 to 16 are typical sectional views of examples of battery caseforming sheets in accordance with the present invention.

Referring to FIG. 13, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a metal foil layer2 and a heat-adhesive resin layer 3 consisting of a polyolefin resinlayer 3 a and an acid-denatured polyolefin resin layer 3 b. The firstbase film layer 1 a is the outermost layer. The right end edge, asviewed in FIG. 13, of the metal foil layer 2 lies on the inner side ofend edges of the other layers and is not exposed on an end edge of thebattery case forming sheet 10.

When the battery case forming sheet 10 is used so that an end edge partthereof in which the end edge of the metal foil layer lies on the innerside of the edges of the other layers corresponds to an open end part ofthe battery case 51, the tabs 59 and 60 will not be short-circuited bythe metal foil layer 2 even if the tabs 59 and 60 extending outside fromthe battery case 51 are bent, which improves the safety of the batterycase 51.

Preferably, the first base film layer 1 a is a PET film, an ON film oran OPP film. Preferably, the metal foil layer 2 is, for example, analuminum foil. It is particularly preferable that the acid-denaturedpolyolefin resin layer 3 b (the innermost layer of the sheet) of theheat-adhesive resin layer 3 is a layer of an acid-denatured polyolefinresin having an acid content in the range of 0.01 to 10% by weight.

The first base film layer 1 a forming the outermost layer of the batterycase forming sheet 10 provides the battery case forming sheet 10 withvarious kinds of mechanical strength including tensile strength,piercing strength and bending strength, and various kinds of resistanceincluding abrasion resistance, water resistance, chemical resistance,heat resistance and low-temperature resistance. The metal foil layer 2serving as an intermediate layer (such as an aluminum foil layer) servesas a barrier layer impermeable to moisture and gases. As mentionedabove, the polyolefin resin layer 3 a and the acid-denatured polyolefinresin layer 3 b of the heat-adhesive resin layer 3 provide the batterycase forming sheet 10 with excellent heat-sealable property and have alow moisture content.

If the metal foil layer is a 9 μm thick aluminum foil, the metal foillayer has a water vapor permeability of 0.01 g/m²·24 hr or below at 40°C. and 90% RH. The water vapor impermeability can easily be enhanced.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/Polyethylene layer (30 μm thick)/Acid-denatured polyolefin resinlayer (10 μm thick)

{circle around (2)} ON film (15 μm thick)/Aluminum foil (9 μmthick)/Polyethylene layer (30 μm thick)/Acid-denatured polyolefin resinlayer (10 μm thick)

{circle around (3)} OPP film (25 μm thick)/Aluminum foil (9 μmthick)/Polyethylene layer (30 μm thick)/Acid-denatured polyolefin resinlayer (10 μm thick)

Referring to FIG. 14, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a second base film1 b, a metal foil layer 2 and a heat-adhesive resin layer 3 consistingof a polyolefin resin layer 3 a and an acid-denatured polyolefin resinlayer 3 b. The first base film layer 1 a is the outermost layer. Theright end edge, as viewed in FIG. 14, of the metal foil layer 2 lies onthe inner side of end edges of the other layers and is not exposed on anend edge of the battery case forming sheet 10.

The battery case forming sheet 10, as compared with the sheet 10 shownin FIG. 13, is provided additionally with the second base film 1 b toimprove the ability of the first base film 1 a on the outer side of themetal foil layer 2, and a two-layer base film is formed by the firstbase film layer 1 a and the second base film layer 1 b.

Each of the first base film layer 1 a and the second base film layer 1 bis a PET film, an ON film or an OPP film. Although the first base filmlayer 1 a and the second base film layer 1 b may be the same types offilms, it is preferable to use different types of films, such as a PETfilm and an ON film as the first base film layer 1 a and the second basefilm layer 1 b, respectively, in view of making the respectiveproperties of the first base film layer 1 a and the second base filmlayer 1 b complement each other.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/ON film (15 μmthick)/Aluminum foil (9 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

{circle around (2)} ON film (15 μm thick)/PET film (12 μmthick)/Aluminum foil (9 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

{circle around (3)} PET film (12 μm thick)/OPP film (25 μmthick)/Aluminum foil (9 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

{circle around (4)} ON film (15 μm thick)/OPP film (25 μmthick)/Aluminum foil (9 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

The base film layers of the battery case forming sheet 10 of thisconstruction on the outer side of the aluminum foil layer have both theadvantages of the PET film and the ON film. Thus, the outer surface ofthe battery case forming sheet 10 has enhanced various kinds ofmechanical strength and resistance, and has generally excellentproperties.

Referring to FIG. 15, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a metal foil layer2, a third base film 1 c and a heat-adhesive resin layer 3 consisting ofa polyolefin resin layer 3 a and an acid-denatured polyolefin resinlayer 3 b. The first base film layer 1 a is the outermost layer.

The battery case forming sheet 10, as compared with the battery caseforming sheet 10 shown in FIG. 13, is provided additionally with thethird base film 1 c sandwiched between the intermediate metal foil layer2 and the heat-adhesive resin layer 3 (directly, the polyolefin resinlayer 3 a) to provided the sheet 10 with stabler barrier effect byenhancing the effect of protecting the metal foil layer 2 by sandwichingthe metal foil layer 2 between the first base film layer 1 a and thethird base film layer 1 c.

The right end edge, as viewed in FIG. 15, of the metal foil layer 2 lieson the inner side of end edges of the other layers and is not exposed onan end edge of the battery case forming sheet 10.

Each of the first base film layer 1 a and the third base film layer 1 cis a PET film, an ON film or a OPP film.

The following are representative examples of the foregoing laminatedsheet.

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

{circle around (2)} PET film (12 μm thick)/Aluminum foil (9 μm thick)ION film (15 μm thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

{circle around (3)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/OPP film (25 μm thick)/Polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick)

{circle around (4)} ON film (15 μm thick)/Aluminum foil (9 μm thick)/PETfilm (12 μm thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

{circle around (5)} ON film (15 μm thick)/Aluminum foil (9 μm thick)/OPPfilm (25 μm thick)/Polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick)

The battery case forming sheet 10 is provided additionally with thethird base film 1 c to provide the sheet 10 with improved various kindsof mechanical strength and resistance to detrimental effects. Since themetal foil layer 2 is sandwiched between the first base film layer 1 aand the third base film layer 1 c, the metal foil layer 2 is protectedmore effectively from both external and internal shocks, abrasion,physical actions and chemical actions, and the sheet 10 has a stablerbarrier effect.

Referring to FIG. 16, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, a second base filmlayer 1 b, a metal foil layer 2, a third base film 1 c and aheat-adhesive resin layer 3 consisting of a polyolefin resin layer 3 aand an acid-denatured polyolefin resin layer 3 b. The first base filmlayer 1 a is the outermost layer.

The battery case forming sheet 10, as compared with the battery caseforming sheet 10 shown in FIG. 14, is provided additionally with thethird base film 1 c sandwiched between the metal foil layer 2 and theheat-adhesive resin layer 3 (directly, the polyolefin resin layer 3 a).

The right end edge, as viewed in FIG. 16, of the metal foil layer 2 lieson the inner side of end edges of the other layers and is not exposed onan end edge of the battery case forming sheet 10. Each of the first basefilm layer 1 a, the second base film layer 1 b and the third base filmlayer 1 c is a PET film, an ON film or an OPP film.

The battery case forming sheet 10 additionally provided with the thirdbase film layer 1 c has improved various kinds of mechanical strengthand resistance to detrimental effects. Since the metal film layer 2 issandwiched between the laminated layer of the first base film layer 1 aand the second base film layer 1 b, and the third base film layer 1 c,the metal foil layer 2 is further effectively protected for the stablerbarrier effect.

When printing a picture of letters and patterns on the surface of eachof the battery case forming sheets 10 shown in FIGS. 13 to 16, thepicture is printed on the inner surface of the first base film layer 1 ato be bonded to the surface of the adjacent layer for second-surfacedecoration, and then the first base film layer is laminated to theadjacent layer. The thus printed picture will not be damaged even if thesurface of the sheet 10 is abraded.

As is apparent form the foregoing description, the present inventionprovides lightweight, thin, flexible, battery case forming sheetsexcellent in various kinds of mechanical strength, resistance todetrimental effects, impermeability to moisture and gases,heat-sealability and processability, and capable of protecting thecomponent parts of a battery contained in a battery case formed byprocessing the battery case forming sheet from the effect of moisture,of preventing short-circuiting the terminals of the battery by the metalfoil layer thereof, of securing safety and of being efficientlyproduced.

Fifth Embodiment

A fifth embodiment according to the present invention will be describedwith reference to FIGS. 17 to 20. A battery case forming sheet in thefifth embodiment is any one of the following laminated sheets (1) to(4), each of a first base film layer and a third base film layer of thebattery case forming sheet is a biaxially oriented polyethyleneterephthalate film, a biaxially oriented nylon film or a biaxiallyoriented polypropylene film, and an acid-denatured polyolefin resinlayer serving as the innermost layer of the sheet contains one or someof an antiblocking agent, a lubricant and a slipping agent. The batterycase forming sheet in the fifth embodiment is substantially the same inother respects as that in the second embodiment.

(1) First base film layer/Metal foil layer/Acid-denatured polyolefinresin layer (innermost layer)

(2) First base film layer/Metal foil layer/Polyolefin resinlayer/Acid-denatured polyolefin resin layer (innermost layer)

(3) First base film layer/Metal foil layer/Third base filmlayer/Acid-denatured polyolefin resin layer (innermost layer)

(4) First base film layer/Metal foil layer/Third base filmlayer/Polyolefin resin layer/Acid-denatured polyolefin resin layer(innermost layer)

When necessary, an adhesive layer, not shown, is formed between theadjacent layers of the laminated sheets (1) to (4).

The heat-adhesive resin layer for heat-sealing (sealant layer) in eachof the laminated sheets (1) and (3) is a single-layer structure of anacid-denatured polyolefin resin layer, and the heat-adhesive resin layerof each of the laminated sheets (2) and (4) is a two-layer laminatedsheet consisting of a polyolefin resin layer and an acid-denaturedpolyolefin resin layer serving as the innermost layer.

In the following description, biaxially oriented polyethyleneterephthalate films, biaxially oriented nylon films and biaxiallyoriented polypropylene films are designated as PET films, ON films andOPP films, respectively.

The metal foil layer i.e., an intermediate layer, serves as an excellentbarrier layer impermeable to moisture and gases. The metal foil layer isprotected by one or both of the first and the third base film layer,i.e., one or some of PET films ON films and OPP films, fissures andpinholes will not be formed in the metal foil layer, and hence thelaminated sheet is provided with various kinds of strength andresistance to detrimental effects.

The innermost sealant layer is a single-layer structure of anacid-denatured polyolefin resin layer or a two-layer laminated sheet ofa polyolefin resin layer and an acid-denatured polyolefin resin layer.

In either case, the innermost layer is the acid-denatured polyolefinresin layer. The acid-denatured polyolefin resin layer is heat-adhesivenot only to itself, but also to metals, such as copper and aluminum.Since the acid-denatured polyolefin resin layer contains one or some ofan antiblocking agent, a lubricant and the slipping agent, the batterycase forming sheet is satisfactory in slipping and antiblockingproperties

Accordingly, the battery case forming sheet can easily resin layercontains one or some of an antiblocking agent, a lubricant and theslipping agent, the battery case forming sheet is satisfactory inslipping and antiblocking properties.

Accordingly, the battery case forming sheet can easily be processed andcan satisfactorily be heat-sealed when processing the same to form abattery case, one end of the battery case can easily be opened whenassembling the component parts of a battery in the battery case, and theopen end part of the battery case through which the tabs 59 and 60extend can satisfactorily be heat-sealed.

The sealant layer of a two-layer laminated sheet consisting of apolyolefin resin layer and an acid-denatured polyolefin resin layer hasan excellent heat-adhesive property. Since the acid-denatured polyolefinresin layer having a relatively high hygroscopic property may be thin,the amount of moisture contained in the acid-denatured polyolefin resinlayer is small, and the component materials of the battery will notadversely be affected by the moisture contained in the acid-denaturedpolyolefin resin layer.

Since the acid-denatured polyolefin resin layer is thin, the amount ofthe acid-denatured polyolefin resin and the amount of the antiblockingagent, the lubricant and/or the slipping agent contained in theacid-denatured polyolefin resin layer are small and material costs arelow, which is economically advantageous.

The metal foil layer is formed so that at least one end edge of themetal foil layer lies on the inner side of the end edges of the otherlayers and is not exposed on the end edge of the battery case formingsheet.

When the battery case forming sheet 10 is used so that an end edge partthereof in which the end edge of the metal foil layer lies on the innerside of the edges of the other layers corresponds to an open end part ofthe battery case, the tabs 59 and 60 will not be short-circuited by themetal foil layer even if the tabs 59 and 60 extending outside from thebattery case are bent, which improves the safety of the battery case.

Materials of the battery case forming sheet and a method ofmanufacturing the battery case forming sheet will be describedhereinafter.

As mentioned above, the battery case forming sheet in accordance withthe present invention has the metal foil layer having excellentimpermeability to moisture and gases as an intermediate layer, the firstbase film layer is formed on the outer surface of the metal foil layeror the first and the third base film layer are formed on the oppositesurfaces of the metal foil layer, a sealant layer, such as anacid-denatured polyolefin resin layer or a laminated sheet of anacid-denatured polyolefin resin layer and a polyolefin resin layer, isformed on the inner side of the metal foil layer, and the acid-denaturedpolyolefin resin layer serving as the innermost layer contains anantiblocking agent, a lubricant and/or a slipping agent.

The metal foil layer, i.e., the intermediate layer, serving as agas-impermeable barrier layer may be an aluminum foil or a copper foil.An aluminum foil is most preferable because the same is inexpensive andis excellent in processability. A suitable thickness of the metal foillayer is in the range of 5 to 25 μm.

The first and the third base film layer may be, for example, some of PETfilms, ON films, OPP films, polyethylene naphthalate films, polyimidefilms and polycarbonate films. In view of various kinds of strength andresistance, ability including durability, processability and economiceffect, PET films, ON films and OPP films are most suitable.

Particularly, PET films have a low hygroscopic property, are excellentin rigidity, tensile strength, bending strength, impact strength,abrasion resistance, heat resistance and water resistance. Thus, PETfilms have a generally balanced ability and have few drawbacks.

ON films have a relatively high hygroscopic property though, ON filmsare flexible and are excellent in piercing strength, impact strength,bending strength and low-temperature resistance.

OPP films are excellent in moisture-proof property, water-proofproperty, chemical resistance, tensile strength and-bending strength.Particularly, the low cost is a significant advantage of OPP films.

The thicknesses of the base films are in the range of 5 to 100 μm, morepreferably, in the range of 12 to 30 μm.

It is preferable, as mentioned above, that the sealant layer, i.e.,the.innermost layer, is heat-adhesive not only to itself, but also tometals forming terminals and have a low hygroscopic property to protectthe component materials of a battery contained in a battery case formedby processing the battery case forming sheet from the adverse effect ofmoisture.

To meet such requirements, the present invention uses an acid-denaturedpolyolefin resin layer or a laminated layer of a polyolefin resin layerand an acid-denatured polyolefin resin layer (innermost layer), and addsan antiblocking agent, a lubricant and/or a slipping agent to theacid-denatured polyolefin resin layer serving as the innermost layer toimprove the slipping and antiblocking properties of the acid-denaturedpolyolefin resin layer.

The polyolefin resin layer of the sealant layer may be formed of, forexample, one of polyethylene resins, polypropylene resins,ethylene-propylene copolymers, ethylene-α-olefin copolymers,ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers,ethylene-methacrylate copolymers, terpolymers of those resins, andresins prepared by blending some of those resins.

The acid-denatured polyolefin resin layer of the sealant layer may beformed of, for example, one of ethylene-acrylic acid copolymers,ethylene-methacrylic acid copolymers, and resins produced by the graftcopolymerization of polyolefin resins, such as polyethylene resins,polypropylene resins, ethylene-propylene copolymers, ethylene-α-olefincopolymers, ethylene-vinyl acetate copolymers, ethylene-acrylatecopolymers, ethylene-methacrylate copolymers and terpolymers of thoseresins, and modifying resins produced by copolymerization by some ofunsaturated carboxylic acids and anhydrides of unsaturated carboxylicacids, such as acrylic acid, methacrylic acid, maleic acid, maleicanhydride, citraconic anhydride, itaconic acid and itaconic anhydride.An acid-denatured polyolefin resin layer having an acid content in therange of 0.01 to 10% by weight is excellently heat-adhesive not only toitself, but also to metals, has a satisfactory film forming property andis easy to use.

The heat-adhesion of the resin to a metal is insufficient if the acidcontent is less than 0.01% by weight, and the film forming performanceof the resin is inferior if the acid content is higher than 10% byweight.

Ionomers produced by cross-linking the resins having carboxyl groupsincluded in those resins by Na⁺ ions or Zn²⁺ ions are suitable materialsfor forming the heat-adhesive resin layer.

The thickness of the sealant layer is in the range of 10 to 120 μm,preferably, in the range of 20 to 100 μm.

When the sealant layer is a two-layer laminated sheet consisting of apolyolefin resin layer and an acid-denatured polyolefin resin layer, theacid-denatured polyolefin resin layer may be thin and the thickness maybe 1 μm or above. Suppose that the thickness of the sealant layer is 100μm, the thickness of the acid-denatured polyolefin resin layer may be inthe range of 1 to 50 μm, preferably, in the range of 5 to 25 μm.

The acid-denatured polyolefin resin layer is soft and self-adhesive.Therefore, the battery case forming sheet has a low slipping propertyand the inner surfaces of a pouch formed by processing the battery caseforming sheet adhere to each other.

The present invention adds an antiblocking agent, a lubricant and/or aslipping agent to the acid-denatured polyolefin resin layer, i.e., theinnermost layer, to solve such a problem.

The antiblocking agent, the lubricant and the slipping agent may beknown ones. Suitable antiblocking agents are silica, zeolite, talc,diatomaceous earth, dicarboxylate amide and polyethylene, suitablelubricant are stearyl alcohol and a fluorocarbon elastomer, and suitableslipping agents are stearic acid amide, oleic acid amide, erucic acidamide and ethylene-bisstearic acid amide.

The respective contents of those additives cannot impartially bedetermined. If only silica is added to the acid-denatured polyolefinresin, suitable ratio of silica to the resin is 0.2 to 0.5 parts byweight silica to 100 parts by weight resin. If a fatty acid amide, suchas stearic acid amide or oleic acid amide, is used suitable ratio of thefatty acid amide to the resin is 0.5 to 1.0 parts by weight fatty acidamide to 100 parts by weight resin.

A method of manufacturing the laminated sheet for forming a battery casewill be described hereinafter.

The metal foil layer, i.e., the intermediate layer, and the first or thethird base film layer may be laminated by a known dry lamination methodusing, for example, two-component polyurethane adhesive, or by anextrusion lamination method which extrudes a molten heat-adhesive resin,such as a polyethylene resin, in a heat-adhesive resin layer between thecomponent layers to be laminated and compresses a laminated sheet of thecomponent layers and the heat-adhesive resin layer sandwiched betweenthe component layers.

The sealant layer is formed on a surface of a laminated sheet consistingof the base film layer and the metal foil layer; that is, the sealantlayer is formed on a surface of the metal foil layer or a surface of thesecond base film layer. The surface to which the sealant layer is bondedmay be coated with an anchor coat (primer coat). An acid-denaturedpolyolefin resin containing an antiblocking agent and/or other additivesis extruded in a desired thickness by extrusion, or a polyolefin resinand an acid-denatured polyolefin resin containing an antiblocking agentand/or other additives are extruded in desired thicknesses,respectively, by coextrusion on the surface of the metal foil layer orthe second base film layer. The sealant layer can be formed in a desiredthickness by a tubular film extrusion method or a multilayer tubularfilm extrusion method and may be laminated to the metal foil layer orthe base film layer by a dry lamination method or an extrusionlamination method.

A battery case forming sheet having a metal foil layer not exposed inthe edges thereof can easily be manufactured by laminating the first orthe third base film and a metal foil so that the opposite end edges ofthe metal foil are about 10 mm on the inner side of the correspondingend edges of the base film, and trimming the opposite end edge parts ofthe base film along lines 1 to 2 mm on the outer side of the oppositeend edges of the metal foil.

Examples of the fourth embodiment will concretely be describedhereinafter with reference to the drawings.

Examples shown in the drawings are illustrative and not limitative. Likeor corresponding parts are designated by the same reference charactersthroughout the drawings.

FIGS. 17 to 20 are typical sectional views of examples of battery caseforming sheets in accordance with the present invention.

Referring to FIG. 17, a battery case forming sheet 10 is formed bysequentially laminating a first base film layer 1 a, i.e., the outermostlayer, an adhesive layer 5 a, a metal foil layer 2, an adhesive layer 5b and a sealant layer 3, the innermost layer of an acid-denaturedpolyolefin resin containing one or some of an antiblocking agent, alubricant and a slipping agent. The right end edge, as viewed in FIG.17, of the metal foil layer 2, i.e., an intermediate layer, lies on theinner side of end edges of the other layers and is not exposed on an endedge of the battery case forming sheet 10.

Referring to FIG. 18, a battery case forming sheet 10 is different fromthe battery case forming sheet 10 shown in FIG. 17 only in that thebattery case forming sheet 10 shown in FIG. 18 has a sealant layer 3,i.e., the innermost layer, consisting of a polyolefin resin layer 3 a,and an acid-denatured polyolefin resin layer 3 b containing one or someof an antiblocking agent, a lubricant and a slipping agent. The batterycase forming sheet 10 shown in FIG. 18 is formed by sequentiallylaminating a first base film layer 1 a, an adhesive layer 5 a, a metalfoil layer 2, an adhesive layer 5 b and the sealant layer 3 consistingof a polyolefin resin layer 3 a, and an acid-denatured polyolefin resinlayer 3 b containing one or some of an antiblocking agent, a lubricantand a slipping agent.

The right end edge, as viewed in FIG. 18, of the metal foil layer 2 lieson the inner side of end edges of the other layers and is not exposed onan end edge of the battery case forming sheet 10.

Referring to FIG. 19, a battery case forming sheet 10 has, in additionto the components of the battery case forming sheet 10 shown in FIG. 17,a third base film layer 1 c sandwiched between the metal foil layer 2and the sealant layer 3 of the acid-denatured polyolefin resincontaining one or some of an antiblocking agent, a lubricant and aslipping agent. The battery case forming sheet 10 is formed bysequentially laminating a first base film layer 11, i.e., the outermostlayer, an adhesive layer 5 a, a metal foil layer 2, an adhesive layer 5b, a third base film layer 1 c and a sealant layer 3 of anacid-denatured polyolefin resin containing one or some of anantiblocking agent, a lubricant and a slipping agent.

The right end edge, as viewed in FIG. 19, of the metal foil layer 2 lieson the inner side of end edges of the other layers and is not exposed onan end edge of the battery case forming sheet 10.

Referring to FIG. 20, a battery case forming sheet 10 is different fromthe battery case forming sheet 10 shown in FIG. 19 only in that thebattery case forming sheet 10 shown in FIG. 20 has a sealant layer 3,i.e., the innermost layer, consisting of a polyolefin resin layer 3 a,and an acid-denatured polyolefin resin layer 3 b containing one or someof an antiblocking agent, a lubricant and a slipping agent. The batterycase forming sheet 10 shown in FIG. 20 is formed by sequentiallylaminating a first base film layer 1 a, i.e., the outermost layer, anadhesive layer 5 a, a metal foil layer 2, an adhesive layer 5 b, a thirdbase film layer 1 c, a polyolefin resin layer 3 a, and an acid-denaturedpolyolefin resin layer 3 b containing one or some of an antiblockingagent, a lubricant and a slipping agent.

The right end edge, as viewed in FIG. 20, of the metal foil layer 2 lieson the inner side of end edges of the other layers and is not exposed onan end edge of the battery case forming sheet 10.

In the battery case forming sheets 10 shown in FIGS. 17 to 20, it ispreferable that each of the first base film layers 1 a and the thirdbase film layers 1 c is a PET film, an ON film or an OPP film, and themetal foil layers 2 are aluminum foils.

The adhesive layer 5 a sandwiched between the first base film layer 1 aand the metal foil layer 2 is capable of satisfactorily bonding togetherthe first base film layer 1 a and the metal foil layer 2. The adhesivelayer 5 a is a layer of a two-component polyurethane adhesive when thefirst base film layer 1 a and the metal foil layer 2 are laminated by adry lamination method, and the adhesive layer 5 a is a layer of aheat-adhesive resin, such as a polyethylene resin, when the first basefilm layer 1 a and the metal foil layer 2 are laminated by an extrusionlamination method.

When the battery case forming sheet 10 is used so that an end edge partthereof in which the end edge of the metal foil layer lies on the innerside of the edges of the other layers corresponds to an open end part ofthe battery case 51, the tabs 59 and 60 will not be short-circuited bythe metal foil layer 2 even if the tabs 59 and 60 extending outside fromthe battery case 51 are bent, which improves the safety of the batterycase 51.

In the battery case forming sheets 10 shown in FIGS. 17 and 18, theadhesive layer 5 b formed on the inner surface of the metal foil layer2, i.e., a surface on the side of the sealant layer 3, attaches thesealant layer 3 firmly to the metal foil layer 2. When forming thesealant layer 3 on the metal foil layer 2 by an extrusion coating methodor a multilayer coextrusion coating method, an anchor coat layer is usedas the adhesive layer 5 b. When forming the sealant layer 3 bylaminating a film to the metal foil layer 2 by a dry lamination methodor an extrusion lamination method, an adhesive layer for dry laminationor a heat-adhesive resin layer, such as a polyethylene resin layer, isused as the adhesive layer 5 b.

In the battery case forming sheets 10 shown in FIGS. 19 and 20, theadhesive layer 5 b is sandwiched between the metal foil layer 2 and thethird base film layer 1 c to bond the metal foil layer 2 and the thirdbase film layer 1 c firmly together. The adhesive layer 5 b, similarlyto the adhesive layer 5 a formed on the outer surface of the metal foillayer 2, is formed by a dry lamination method or a multilayercoextrusion lamination method, and is an adhesive layer for drylamination or a heat-adhesive resin layer, such as a polyethylene resinlayer.

In the foregoing battery case forming sheets 10, the sealant layer 3 isattached to the inner surface, i.e., a lower surface as viewed in FIGS.19 and 20, of the third base film layer 1 c. Preferably, an adhesivelayer, not shown, is sandwiched between the third base film layer 1 cand the sealant layer 3. An anchor coat layer, i.e., an adhesive layer,is formed when forming the sealant layer 3 by an extrusion coatingmethod or a multilayer coextrusion coating method an adhesive layer fordry lamination or a heat-adhesive resin layer, such as a polyethyleneresin layer, is formed when forming the sealant layer 3 by laminating afilm of a sealant to the third base film layer 1 c by a dry laminationmethod or an extrusion lamination method.

In the battery case forming sheet 10 shown in FIG. 17, the outermostfirst base film layer 1 a, i.e., a PET film, an ON film or an OPP film,protects the metal foil layer 2, i.e., an intermediate layer, andprovides the battery case forming sheet 10 with mechanical strengthincluding tensile strength, piercing strength and bending strength, andresistance including abrasion resistance, water resistance, chemicalresistance, heat resistance and low-temperature resistance, the metalfoil layer 2, such as an aluminum foil serving as an intermediate layer,provides the battery case forming sheet 10 with excellent impermeabilityto moisture and gases, and the innermost sealant layer 3, i.e., anacid-denatured polyolefin resin layer containing one or some of anantiblocking agent, a lubricant and a slipping agent (hereinafterreferred to as “acid-denatured polyolefin resin layer containing anantiblocking agent”) provides the battery case forming sheet 10 withexcellent heat-adhesive property and satisfactory slipping andantiblocking properties.

Accordingly, the battery case forming sheets can efficiently be joinedtogether by heat-sealing when forming a battery case having the shape ofa pouch having one open end, the open end of case can easily be openedand closed by heat-sealing when putting the component materials of abattery in the battery case and closing the open end of the case, andthe open end of the case through which the tabs 59 and 60 extend outsidefrom the battery case can be sealed by satisfactorily heat-sealing theopen end of the battery case.

Since the metal foil layer 2 of the battery case forming sheet 10 isformed so that at least one end edge thereof lies on the inner side ofthe edges of the other layers and is not exposed on the end edge of thebattery case forming sheet 10, terminals extending outside from thebattery case will not be short-circuited by the metal foil layer 2 evenif the terminals are bent when the battery case forming sheet 10 is usedso that the end part in which the metal foil layer is not exposedcorresponds to the open end of the battery case, which further enhancessafety.

The battery case forming sheet 10 shown in FIG. 18 is provided with thesealant layer 3 of a two-layer laminated sheet consisting of apolyolefin resin layer 3 a and an acid-denatured polyolefin resin layercontaining an antiblocking agent instead of the sealant layer 3 of theacid-denatured polyolefin resin layer containing an antiblocking agentemployed in the battery case forming sheet shown in FIG. 17.

Therefore, the battery case forming sheet 10 shown in FIG. 18 has theexcellent heat-adhesive, slipping and antiblocking properties inaddition to the effects of the battery case forming sheet 10 shown inFIG. 17, the amount of moisture contained in the acid-denaturedpolyolefin resin layer 3 b containing an antiblocking agent is smalleven if the acid-denatured polyolefin resin layer 3 b containing anantiblocking layer 3 b absorbs moisture because the acid-denaturedpolyolefin resin layer 3 b containing an antiblocking agent can beformed in the least necessary thickness, and the component materials ofthe battery will not adversely be affected by the moisture contained inthe acid-denatured polyolefin resin layer 3 b.

The battery case forming sheet 10 shown in FIG. 19 has, in addition tothe components of the battery case forming sheet 10 shown in FIG. 17,the third base film layer 1 c sandwiched between the metal foil layer 2and the sealant layer 3 of the acid-denatured polyolefin resincontaining an antiblocking agent, and the battery case forming sheet 10shown in FIG. 20 has, in addition to the components of the battery caseforming sheet 10 shown in FIG. 18, the third base film layer 1 csandwiched between the metal foil layer 2 and the polyolefin resin layer3 a of the sealant layer 3.

The additional third base film layers 1 c of the battery case formingsheets 10 shown in FIGS. 19 and 20 provide the battery case formingsheets 10 shown in FIGS. 19 and 20 with various kinds of strength andresistance higher than those of the battery case forming sheets 10 shownin FIGS. 17 and 18. Since the metal foil layer 2 is protected securelyby the first base film layer 1 a and the third base film layer 1 cextending on the opposite sides thereof, the metal foil layer 2 is ableto exercise its excellent impermeability to moisture and gases stablywith higher reliability.

Particularly, when a PET film having a low hygroscopic property andexcellent in various kinds of strength and resistance, particularly, inheat resistance is used as the third base film layer 1 c, the PET filmwill neither broken nor torn even if the same is exposed to a hightemperature and a high pressure and is capable of protecting the metalfoil layer 2 with reliability and therefore a battery case forming sheetcan safely be heat-sealed when forming a battery case.

If the metal foil layer is a 9 μm thick aluminum foil, the metal foillayer has a water vapor permeability of 0.01 g/m²·24 hr or below at 40°C. and 90% RH. The water vapor impermeability can easily be enhanced.

The following are representative examples of the foregoing laminatedsheets shown in FIGS. 17 to 20.

Laminated sheet Shown in FIG. 17

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/Acid-denatured polyolefin resin layer (50 μm thick) (innermostlayer)

{circle around (2)} ON film (15 μm thick)/Aluminum foil (9 μmthick)/Acid-denatured polyolefin resin layer (50 μm thick) (innermostlayer)

{circle around (3)} OPP film (20 μm thick)/Aluminum foil (9 μmthick)/Acid-denatured polyolefin resin layer (50 μm thick) (innermostlayer)

Laminated sheet Shown in FIG. 18

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/Polyolefin layer (35 μm thick)/Acid-denatured polyolefin resinlayer (15 μm thick) (innermost layer)

{circle around (2)} ON film (15 μm thick)/Aluminum foil (9 μmthick)/Polyolefin layer (35 μm thick)/Acid-denatured polyolefin resinlayer (15 μm thick) (innermost layer)

{circle around (3)} OPP film (20 μm thick)/Aluminum foil (9 μmthick)/polyolefin layer (35 μm thick)/Acid-denatured polyolefin resinlayer (15 μm thick) (innermost layer)

Laminated sheet Shown in FIG. 19

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Acid-denatured polyolefin resin layer (40μm thick) (innermost layer)

{circle around (2)} ON film (15 μm thick)/Aluminum foil (9 μm thick)/PETfilm (12 μm thick)/Acid-denatured polyolefin resin layer (40 μm thick)(innermost layer)

{circle around (3)} OPP film (20 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Acid-denatured polyolefin resin layer (40μm thick) (innermost layer)

Laminated sheet Shown in FIG. 20

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Polyethylene resin layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick) (innermostlayer)

{circle around (2)} ON film (15 μm thick)/Aluminum foil (9 μm thick)/PETfilm (12 μm thick)/Polyethylene resin layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick) (innermost layer)

{circle around (3)} OPP film (20 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/polyethylene layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick) (innermostlayer)

{circle around (4)} PET film (12 μm thick)/Aluminum foil (9 μm thick)/ONfilm (12 μm thick)/polyethylene layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick) (innermost layer)

When printing a picture of letters and patterns on the surface of eachof the battery case forming sheets 10 shown in FIGS. 17 to 20, thepicture is printed on the inner surface of the first base film layer 1 ato be bonded to the surface of the adjacent layer for second-surfacedecoration, and then the first base film layer is laminated to theadjacent layer. The thus printed picture will not be damaged even if thesurface of the sheet 10 is abraded.

As is apparent form the foregoing description, the present inventionprovides lightweight, thin, flexible, battery case forming sheets havingprincipal layers of plastic material, excellent in various kinds ofmechanical strength, resistance to detrimental effects, impermeabilityto moisture and gases, heat-sealability and heat-adhesion to terminalsformed of metal foils or the like, capable of preventingshort-circuiting terminals, of being easily processed and of beingefficiently produced, and provided with a sealant layer having a lowhygroscopic property and satisfactory in slipping and antiblockingproperties.

Sixth Embodiment

A sixth embodiment according to the present invention will be describedwith reference to FIGS. 21 to 23. A battery case forming sheet in thesixth embodiment is any one of the following laminated sheets (1) to(3). Battery case forming sheets in the sixth embodiment aresubstantially the same as those in the first embodiment, except that thebattery case forming sheets in the sixth embodiment employ polyolefinresin layers of thicknesses in the range of 10 to 100 μm to be laminatedto one or both the surfaces of a metal foil layer.

(1) First base film layer/Metal foil layer/Acid-denatured polyolefinresin layer (innermost layer)

(2) First base film layer/Metal foil layer/Polyolefin resin layer/Thirdbase film layer/Heat-adhesive resin layer (innermost layer)

(3) First base film layer/Polyolefin resin layer/Metal foillayer/Polyolefin resin layer/Third base film layer/Heat-adhesive resinlayer (innermost layer)

The metal foil layer, i.e., an intermediate layer, provides the batterycase forming sheet with impermeability to moisture and gases, the firstand the third base film layers provides the battery case forming sheetwith various kinds of strength and resistance and protect the metal foillayer from actions tending to cause fissures and pinholes in the metalfoil layer in order that the metal foil layer is able to maintain itsbarrier property.

A polyolefin resin layer is formed in a thickness in the range of 10 to100 μm on one or both of the surfaces of the metal foil layer. Thepolyolefin resin forming the polyolefin resin layer is highlyheat-adhesive, have a relatively low melting point or softening pointand is excellent in heat-fluidity.

Therefore, when forming a battery case by heat-sealing end edge part ofthe laminated sheet, a high temperature and a high pressure are appliedparticularly to the end edge parts to heat-seal an open end of thebattery case. Since the polyolefin resin becomes fluidic when heated andhas a sufficient thickness, the polyolefin resin layer can beheat-softened and extruded through the edge of the open end of thebattery case so as to cover the metal foil layer exposed on the edge ofthe open end.

Consequently, the tabs 59 and 60 extending from the battery case so asto extend outside the battery case will not come into contact with themetal foil layer even if the tabs 59 and 60 are bent, which improves thesafety of the battery case.

Since the innermost layer of the battery case forming sheet is theheat-adhesive resin layer, an open end of a battery case having theshape of a pouch formed by processing the battery case forming sheet caneasily be sealed by heat-sealing after putting the component materialsof a battery in the battery case.

Each of the first base film layers and the third base film layers of theforegoing laminated sheets is a biaxially oriented polyethyleneterephthalate film, a biaxially oriented nylon film or a biaxiallyoriented polypropylene film.

In the following description, biaxially oriented polyethyleneterephthalate films, biaxially oriented nylon films and biaxiallyoriented polypropylene films are designated as PET films, ON films andOPP films, respectively.

The PET films, ON films and OPP films are excellent in strengthincluding tensile strength, bending strength, impact strength andpiercing strength, resistance including water resistance, chemicalresistance, solvent resistance, abrasion resistance, heat resistance andlow-temperature resistance, printability and processability includingease of lamination, and are readily available inexpensive, economicalgeneral-purpose films.

Battery case forming sheets of the foregoing structures having generallyexcellent properties can efficiently be produced at a low cost.

The polyolefin resin layer laminated to the metal foil layer is formedof an acid-denatured polyolefin resin or an ethylene-α-olefin copolymerproduced by polymerization using a single site catalyst.

Acid-denatured polyolefin resins and ethylene-α-olefin copolymersproduced by polymerization using a single site catalyst have meltingpoints or softening points lower than those of polyolefin resins, suchas polyethylene resins and polypropylene resins, and become fluidic whenheated. Therefore, acid-denatured polyolefin resins andethylene-α-olefin copolymers produced by polymerization using a singlesite catalyst can easily be heat-softened and extruded through the edgeof the open end of the battery case so as to cover the metal foil layerexposed on the edge of the open end when the end edge parts of the sheetare heat-sealed.

Since acid-denatured polyolefin resins are particularly excellent inheat-adhesiveness to metals, an acid-denatured polyolefin resin layercan firmly be laminated to a metal foil layer by an extrusion laminationmethod. Since ethylene-α-olefin copolymers produced by polymerizationusing a single site catalyst have a narrow molecular weight distributionand a stable copolymerization ratio, and are excellent inlow-temperature heat-sealability and hot-sealability, ethylene-α-olefincopolymers produced by polymerization using a single site catalyst caneasily be extruded through the end edges of the sheet duringheat-sealing and can properly be used for covering end edges of themetal foil.

The heat-adhesive resin layer, i.e., the innermost layer of thelaminated sheet, may be either a single-layer structure of anacid-denatured polyolefin resin layer or a two-layer laminated sheet ofa polyolefin resin layer and an acid-denatured polyolefin resin layer.

The heat-adhesive resin layer, i.e., the innermost layer of thelaminated sheet, may be formed of any one of polyethylene resins andpolyolefin resins. Acid-denatured polyolefin resins are heat-adhesivenot only to themselves, but also to metals.

When the heat-adhesive resin layer is only an acid-denatured polyolefinresin layer, an open end of a battery case having the shape of a pouchformed by processing the battery case forming sheet can easily be sealedby heat-sealing even if terminals formed of bear metal foils areextended through the open end of the pouch.

When heat-adhesive resin layer is a two-layer laminated sheet of apolyolefin resin layer and an acid-denatured polyolefin resin layer, theacid-denatured polyolefin resin layer may be very thin. Therefore, theamount of moisture contained in the acid-denatured polyolefin resinlayer is very small even if the acid-denatured polyolefin resin layerabsorbs moisture during storage, and hence the acid-denatured polyolefinresin layer maintains a satisfactory hat-adhesiveness to the metalforming the terminals and the component materials of the batterycontained in the battery case can be protected from the adverse effectof moisture.

Materials for manufacturing the battery case sheet in accordance withthe present invention and methods of processing the materials will bedescribed hereinafter.

The battery case forming sheet according to the present invention has,as an intermediate layer, the metal foil layer highly impermeable tomoisture and gases, a polyolefin resin layer of a thickness in the rangeof 10 to 100 μm is laminated to one or both the surfaces of the metalfoil layer, the first or the third base film layer excellent in variouskinds of strength and resistance is attached to the opposite sides ofthe intermediate layer, and the heat-adhesive resin layer is formed asthe innermost layer.

An aluminum foil and a copper foil are suitable materials for formingthe gas-impermeable metal foil layer, i.e., the intermediate layer. Analuminum foil is the most preferable material for forming the metal foillayer because an aluminum foil is inexpensive, easy to process and easyto bond to a film.

A suitable thickness of the metal foil layer is in the range of 5 to 25μm. A metal foil layer of a thickness less than 5 μm is undesirablebecause many pinholes are liable to be formed in such a thin metal foillayer to reduce the barrier property of the metal foil layer. A metalfoil layer of a thickness above 25 μm is excessively thick, subject toplastic deformation and economically disadvantageous.

For example, if a 9 μm thick aluminum foil is used for forming the metalfoil layer, the metal foil layer has a satisfactorily low water vaporpermeability less than 0.01 g/m²·24 hr or below at 40° C. and 90% RH.The moisture impermeability of the metal foil layer can easily beenhanced.

As mentioned above, the polyolefin resin layer contiguous with the metalfoil layer is extruded through the edge of the open end of the batterycase so as to cover the metal foil layer exposed on the edge of the openend when the end edge parts of the sheet are heat-sealed. Therefore, apreferable thickness of the polyolefin resin layer is in the range of 10to 100 μm.

A polyolefin resin layer of a thickness less than 10 μm is undesirablebecause it is difficult to extrude such a thin polyolefin resin layerthrough the edge of the open end of the battery case so as to cover themetal foil layer. A polyolefin resin layer of a thickness over 100 μm isexcessively thick, takes much time for heating the same by conductionfor heat-sealing, reduces productivity and is economicallydisadvantageous.

The polyolefin resin layer must have satisfactory hot-fluidity and highhot-adhesiveness as well as an appropriate thickness. Suitable materialsfor forming the polyolefin resin layer are polyethylene resins,polyethylene copolymers and blends of olefin elastomers. Preferablepolyethylene resins are those having a density in the range of 0.910 to0.940 g/cm³, and a MFI (melt flow index) in the range of 4.0 to 14.0g/10 min.

When particular importance is attached to hot-fluidity andhot-adhesiveness to metals, it is preferable to form the polyolefinresin layer of some of acid-denatured polyolefin resins andethylene-α-olefin copolymers produced by polymerization using a singlesite catalyst.

The foregoing acid-denatured polyolefin resins are, for example, resinsproduced by modifying ethylene-acrylic acid copolymers,ethylene-methacrylic acid copolymers, polyethylene resins, polypropyleneresins, and resins produced by graft copolymerization includingethylene-propylene copolymers, ethylene-α-olefin copolymers,ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers,ethylene-methacrylate copolymers and terpolymers of those resins by someof unsaturated carboxylic acids and anhydrides of unsaturated carboxylicacids, such as acrylic acid, methacrylic acid, maleic acid, maleicanhydride, citraconic anhydride, itaconic acid and itaconic anhydride.

Ionomers produced by cross-linking the resins having carboxyl groupsincluded in those resins by Na⁺ ions or Zn²⁺ ions are suitable materialsfor forming the heat-adhesive resin layer.

A preferable acid content of those acid-denatured polyolefin resins isin the range of 0.01 to 10% by weight. The heat-adhesiveness of theacid-denatured polyolefin resins to metals is insufficient if the acidcontent thereof is less than 0.01% by weight. Acid-denatured polyolefinresins having a acid content exceeding 10% by weight is inferior in filmforming property and is not preferable.

The first and the third base film layer may be, for example, some of PETfilms, ON films, OPP films, polyethylene naphthalate films, polyimidefilms and polycarbonate films. In view of various kinds of strength andresistance, ability including durability, processability and economiceffect, PET films, ON films and OPP films are most suitable.

Although PET films, ON films and OPP films are not particularlydifferent in properties from each other, PET films have low hygroscopicproperty and are excellent in rigidity, tensile strength, abrasionresistance and heat resistance, ON films have relatively highhygroscopic property and are excellent in flexibility, tensile strength,piercing strength, bending strength and low-temperature resistance. OPPfilms have very low hygroscopic property and are excellent inmoisture-proof property, tensile strength and chemical resistance.

Preferably, the thickness of the base films is in the range of 5 to 100μm, more preferably, 12 to 30 μm.

The heat-adhesive resin layer, i.e., the innermost layer, provides thelaminated sheet with a heat-adhesive property necessary for fabricatinga battery case having the shape of a pouch by processing the laminatedsheet. It is preferable that, the heat-adhesive resin layer is basicallyadhesive to itself, is stable and unsusceptible to the swelling andcorrosive actions of an electrolyte contained in the battery case, has alow hygroscopic property, and is capable of isolating the components ofa battery including the electrolyte from the influence of moisture.

In view of such desirable conditions, suitable materials for forming theheat-adhesive resin layer are polyethylene resins, polypropylene resins,ethylene-propylene copolymers, ethylene-α-olefin copolymers,ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers,ethylene-methacrylate copolymers and terpolymers of those resins. Thesematerials may be used individually or in a blend.

As mentioned above, the tabs 59 and 60 extend, in some cases, in an endpart of a battery case to be heat-sealed when sealing the components ofa battery in the battery case. In such a case, the heat-adhesive resinlayer must be heat-adhesive to the tabs 59 and 60.

The acid-denatured polyolefin resins mentioned in the description of thepolyolefin resin layers to be laminated to the metal foil layer areheat-adhesive resins substantially meeting those requirements.

Although acid-denatured polyolefin resins have enhancedheat-adhesiveness to metals, the same are hydrophilic and have arelatively high hygroscopic property.

Therefore, if a heat-adhesive resin layer of an acid-denaturedpolyolefin resin is used as the innermost layer of a battery caseforming sheet, it is possible that the innermost layer absorbs moistureonly a little though when a battery case formed of the battery caseforming sheet and containing a battery therein is stored in a moistenvironment for a long term. Thus, the relatively high hygroscopicproperly of the acid-denatured polyolefin resins is detrimental to thecomponent materials of the battery, such as the electrolyte.

Accordingly, it is preferable to use, as the innermost heat-adhesiveresin layer, an acid-denatured polyolefin resin layer or a laminatedsheet of a polyolefin resin layer and a thin acid-denatured polyolefinresin layer in order that the amount of moisture contained in theacid-denatured polyolefin resin layer is small even if theacid-denatured polyolefin resin layer should absorb moisture.

The polyolefin resin layer may be formed of a resin selected from arelatively large variety of resins, such as polyethylene resins,polypropylene resins, ethylene-propylene copolymers, ethylene-α-olefincopolymers, ethylene-vinyl acetate copolymers, ethylene-acrylatecopolymers, ethylene-methacrylate copolymers and terpolymers of thoseresins. These resins may be used individually or in a blend.

A preferable thickness of the heat-adhesive resin layer is in the rangeof 10 to 100 μm. When a laminated sheet of a polyolefin resin layer andan acid-denatured polyolefin resin layer, a preferable thickness of theacid-denatured polyolefin resin layer is in the range of 1 to 50 μm,more preferably, in the range of 5 to 25 μm.

An acid-denatured polyolefin resin layer of a thickness less than 1 μmdoes not provide sufficient heat-adhesiveness to metals, and anacid-denatured polyolefin resin layer of a thickness over 50 μm is notpreferable because such a thick acid-denatured polyolefin resin layer isable to contain a large amount of moisture.

The first and the third base film layer, the metal foil layer, thepolyolefin resin layer contiguous with the metal foil layer and theheat-adhesive resin layer of the battery case forming sheet can belaminated by properly using well-known methods, such as a extrusionlamination method, a dry lamination method, an extrusion coating methodand multilayer coextrusion coating method.

There is no particular restriction on laminating methods and order oflamination; laminating methods and order of lamination may optionallyand selectively determined taking into consideration the properties ofthe laminated sheet, productivity, loss rate and such.

A battery case forming sheet of a laminated sheet (1) having aconstruction of first base film layer/polyolefin resin layer/metal foillayer/third base film layer/heat-adhesive resin layer (innermost layer)can be fabricated by, for example, extruding a molten polyolefin resinin a predetermined thickness so as to be sandwiched between the firstbase film layer and the metal foil layer by an extrusion laminationmethod, compressing the polyolefin resin layer, the first base filmlayer and the metal foil layer to laminate the same, laminating thethird film layer to the surface of the metal foil layer by a drylamination method, and laminating the heat-adhesive resin layer to thethird base film layer by an extrusion coating method or a multilayercoextrusion coating method.

If the innermost heat-adhesive resin layer is a laminated sheetconsisting of a polyolefin resin layer and an acid-denatured polyolefinresin layer, a laminated film of the polyolefin resin layer and theacid-denatured polyolefin resin layer is formed in a predeterminedthickness by a multilayer tubular film extrusion method, and thepolyolefin resin layer of the laminated film is attached to the thirdbase film layer by a dry lamination method. The same method applies alsoto fabricating the following structures (2) and (3).

If necessary, the surfaces to be bonded together may be coated with ananchor coat (a kind of primer coat) to enhance the adhesion between thebonded layers when carrying out the extrusion lamination method and theextrusion coating method.

A battery case forming sheet of a laminated sheet (2) having aconstruction of first base film layer/metal foil layer/polyolefin resinlayer/third base film layer/heat-adhesive resin layer (innermost layer)can be fabricated by, for example, bonding together the first base filmlayer and the metal foil layer by a dry lamination method, extruding amolten polyolefin resin so as to be sandwiched between the metal foillayer and the third base film layer by an extrusion lamination method,compressing the polyolefin resin layer, the metal foil layer and thethird base film layer to laminate the same, and laminating theheat-adhesive resin layer to the third base film layer by the samemethod as that employed in fabricating the battery case forming sheet ofthe laminated sheet (1).

A battery case forming sheet of a laminated sheet (3) having aconstruction of first base film layer/polyolefin resin layer/metal foillayer/polyolefin resin layer/third base film layer/heat-adhesive resinlayer (innermost layer) is similar in construction to the battery caseforming sheets of the laminated sheets (1) and (2) and can be fabricatedby properly using some of the extrusion lamination method, the drylamination method, the extrusion coating method and the multilayercoextrusion coating method.

In the laminated sheets (1), (2) and (3), the polyolefin resin layer tobe laminated to the metal foil layer may previously be formed in apredetermined thickness by a tubular film extrusion method or the likeand may be bonded to the metal foil layer by a dry lamination method.

Examples of the sixth embodiment will concretely be describedhereinafter with reference to the drawings.

Examples shown in the drawings are illustrative and not limitative. Likeor corresponding parts are designated by the same reference charactersthroughout the drawings.

FIGS. 21 to 23 are typical sectional views of examples of battery caseforming sheets in accordance with the present invention.

A battery case forming sheet 10 shown in FIG. 21 corresponds to thelaminated sheet (1) and is formed by sequentially laminating a firstbase film layer 1 a, i.e., the outermost layer, a polyolefin resin layer6 a, a metal foil layer 2, a third base film layer 1 c and an adhesivelayer 3.

A battery case forming sheet 10 shown in FIG. 22 corresponds to thelaminated sheet (2) and is formed by sequentially laminating a firstbase film layer 1 a, i.e., the outermost layer, a metal foil layer 2, apolyolefin resin layer 6 a, a third base film layer 1 c and an adhesivelayer 3.

A battery case forming sheet 10 shown in FIG. 23 corresponds to thelaminated sheet (3) and is formed by sequentially laminating a firstbase film layer 1 a, i.e., the outermost layer, a polyolefin resin layer6 a, a metal foil layer 2, a polyolefin resin layer 6 b, a third basefilm layer 1 c and an adhesive layer 3.

When forming the battery case forming sheets shown in FIGS. 21 to 23, itis preferable to use PET films, ON films or OPP films to form the firstbase film 1 a and the third base film layer 1 c.

The tabs 59 and 60 of a metal foil or the like extend in an open endpart of a battery case having the shape of a pouch formed by processingthe battery case forming sheets of the present invention and the openend part is heat-sealed under somewhat heavy heat-sealing conditions.Accordingly, the third base film layer 1 c must be strong enough towithstand the tearing action of the tabs 59 and 60 that is exertedthereto during heat-sealing and to protect the metal foil layer, i.e.,an intermediate layer, with reliability and must be excellent inmechanical strength and heat resistance. In view of such conditions, PETfilms are particularly preferable for forming the third base film layer1 c.

The first base film layer 1 a and the third base film layer 1 c may bethe same kind of films or may be different kinds of films.

An aluminum foil is a preferable material for forming the metal foillayer 2. The thicknesses of the polyolefin resin layers 6 a and 6 bcontiguous with the metal foil layer 2 are in the range of 10 to 100 μm.

Although the heat-adhesive resin layer 3 may be a single layer of apolyolefin resin, it is preferable, when the tabs 59 and 60 are baremetal foils, to form the heat-adhesive resin layer 3 of anacid-denatured polyolefin resin highly adhesive to metals. It is morepreferable to form the heat-adhesive resin layer 3 by laminating apolyolefin resin layer and an acid-denatured polyolefin resin layer tolimit the increase of the moisture content of the heat-adhesive resinlayer 3 due to moisture absorption by the acid-denatured polyolefinresin layer to the least possible extent.

The following are representative examples of the foregoing laminatedsheets shown in FIGS. 21 to 23.

Laminated sheet Shown in FIG. 21

{circle around (1)} PET film (12 μm thick)/Acid-denatured polyolefinresin layer (50 μm thick)/Aluminum foil (9 μm thick)/PET film (12 μmthick)/Polyethylene resin layer (30 μm thick)/Acid-denatured polyolefinresin layer (10 μm thick) (innermost layer)

{circle around (2)} ON film (15 μm thick)/Ethylene-α-olefin copolymerlayer produced by using a single site catalyst (50 μm thick)/Aluminumfoil (9 μm thick)/Acid-denatured polyolefin resin layer (10 μm thick)(innermost layer)

{circle around (3)} OPP film (20 μm thick)/Ethylene-α-olefin copolymerlayer produced by using a single site catalyst (50 μm thick)/Aluminumfoil (9 μm thick)/PET film (12 μm thick)/Polyethylene resin layer (30 μmthick)/Acid-denatured polyolefin resin layer (10 μm thick) (innermostlayer)

Laminated sheet Shown in FIG. 22

{circle around (1)} PET film (12 μm thick)/Aluminum foil (9 μmthick)/Acid-denatured polyolefin resin layer (50 μm thick)/PET film (12μm thick)/Polyethylene resin layer (30 μm thick)/Acid-denaturedpolyolefin resin layer (10 μm thick) (innermost layer)

{circle around (2)} ON film (15 μm thick)/Aluminum foil (9 μmthick)/Ethylene-α-olefin copolymer produced by using a single sitecatalyst (50 μm thick)/PET film (12 μm thick)/Polyethylene resin layer(30 μm thick)/Acid-denatured polyolefin resin layer (10 μm thick)(innermost layer)

{circle around (3)} OPP film (20 μm thick)/Aluminum foil (9 μmthick)/Ethylene-α-olefin copolymer produced by using a single sitecatalyst (40 μm thick)Polyolefin layer (35 μm thick)/PET film (12 μmthick)/Polyethylene resin layer (30 μm thick)/Acid-denatured polyolefinresin layer (10 μm thick) (innermost layer)

Laminated sheet Shown in FIG. 23

{circle around (1)} PET film (12 μm thick)/Acid-denatured polyolefinresin layer (30 μm thick)/Aluminum foil (9 μm thick)/Acid-denaturedpolyolefin resin layer (30 μm thick)/PET film (12 μm thick)/Polyethyleneresin layer (30 μm thick)/Acid-denatured polyolefin resin layer (10 μmthick) (innermost layer)

{circle around (2)} ON film (15 μm thick)/Ethylene-α-olefin copolymerproduced by using a XXXX catalyst (30 μm thick)/Aluminum foil (9 μmthick)/Ethylene-α-olefin copolymer produced by using a single sitecatalyst (30 μm thick)/PET film (12 μm thick)/Polyethylene resin layer(30 μm thick)/Acid-denatured polyolefin resin layer (10 μm thick)(innermost layer)

{circle around (3)} OPP film (20 μm thick)/Ethylene-α-olefin copolymerproduced by using a single site catalyst (30 μm thick)/Aluminum foil (9μm thick)/Ethylene-α-olefin copolymer produced by using a single sitecatalyst (30 μm thick)/PET film (12 μm thick)/Polyethylene resin layer(30 μm thick)/Acid-denatured polyolefin resin layer (10 μm thick)(innermost layer)

In the battery case forming sheet 10 thus constructed, the metal foillayer 2, i.e., an intermediate layer, is protected by the first basefilm layer 1 a and the third base film layer 1 c contiguous with theopposite surfaces of the metal foil layer 2. Thus, the first base filmlayer 1 a and the third base film layer 1 c provide the battery caseforming sheet 10 with excellent mechanical strength including tensilestrength, impact strength, piecing strength and bending strength, andresistance including abrasion resistance, water resistance, chemicalresistance, solvent resistance, heat resistance, chemical resistance,heat resistance and low-temperature resistance. The metal foil layer 2,such as an aluminum foil layer, serves as a reliable barrier impermeableto moisture and gases. The heat-adhesive resin layer 4 of anacid-denatured polyolefin resin serving as the innermost layer isadhesive not only to itself, but also to metals. The heat-adhesive layer4 of a laminated sheet consisting of a polyolefin resin layer and anacid-denatured polyolefin resin layer is not only adhesive to itself andto metals, but also is effective in enhancing the moistureimpermeability of the battery case forming sheet 10.

Since the polyolefin resin layer 6 a is sandwiched between the metalfoil layer 2 and the first base film layer 1 a, the polyolefin resinlayer 6 b is sandwiched between the metal foil layer and the third basefilm layer 1 c, or the polyolefin resin layer 6 a is sandwiched betweenthe metal foil layer 2 and the first base film layer 1 a, and thepolyolefin resin layer 6 b is sandwiched between the metal foil layerand the third base film layer 1 c, and the polyolefin resin layers 6 aand 6 b has thicknesses in the range of 10 to 100 μm, part of thepolyolefin resin layer 6 a, part of the polyolefin resin layer 6 b, orpart of the polyolefin resin layers 6 a and 6 b is extruded through theedge of the open end of a pouch formed by processing the battery caseforming sheet so as to cover an end surface of the metal foil layer 2exposed on the edge of the open end only by heat-sealing the end edgeparts of the pouch under slightly heavy heat-sealing conditions.Consequently, the tabs 59 and 60 extending from the battery case so asto extend outside the battery case will not come into contact with themetal foil layer even if the tabs 59 and 60 are bent, which improves thesafety of the battery.

When printing a picture of letters and patterns on the surface of eachof the battery case forming sheets 10 shown in FIGS. 21 to 23, thepicture is printed on the inner surface of the first base film layer 1 ato be bonded to the surface of the adjacent layer for second-surfacedecoration, and then the first base film layer is laminated to theadjacent layer. The thus printed picture will not be damaged even if thesurface of the sheet 10 is abraded and is highly resistant to abrasion.

As is apparent form the foregoing description, the present inventionprovides lightweight, thin, flexible, battery case forming sheetsexcellent in various kinds of mechanical strength, resistance todetrimental effects, impermeability to moisture and gases,heat-sealability and processability, and capable of protecting thecomponent materials of a battery sealed in a battery case formed byprocessing the battery case forming sheet from detrimental effects ofmoisture and of preventing the accidental contact between the terminalsof metal foils extending from the inside of the battery case so as toextend outside the battery case, and the metal foil layer serving as theintermediate layer of the battery case forming sheet even if theterminals are bent and of being efficiently produced.

Seventh Embodiment

A seventh embodiment according to the present invention will bedescribed with reference to FIGS. 24 to 28. Battery case forming sheetsin the seventh embodiment according to the present invention aresubstantially the same as those in the first embodiment excluding thatthe battery case forming sheet in the seventh embodiment is a laminatedsheet formed by laminating at least one kind of base film layer and aheat-adhesive resin layer, and the heat-adhesive resin layer is formedin a pattern.

The battery case forming sheets are put together with the heat-adhesivelayers forming the inner surfaces thereof in contact with each other,and bonded together by, for example, heat-sealing to form a battery casehaving the shape of a pouch having one open end. The component materialsof a polymer battery 50 a are assembled in the battery case, tabs 59 and60 are extended from the inside of the battery case through the open endso as to extend outside the battery case, and then the open end of thebattery case is sealed by heat-sealing to complete a battery.

Although there is not any particular restrictions on the pattern of theheat-adhesive resin layer, the pattern of the heat-adhesive resin layerhas parts of a width corresponding to a heat-sealing width extendingalong the edges of the battery case forming sheet. The heat-adhesiveresin layer can be formed by preparing a dope of a heat-adhesive resin,and printing the dope in a heat-adhesive resin layer of a predeterminedpattern by gravure printing, silk-screen printing or flexographicprinting, and drying the printed heat-adhesive resin layer.

The base film layer provides the battery forming sheet with variouskinds of strength and resistance, and the heat-adhesive resin layerformed in a pattern enables the effective use of the heat-adhesiveresin, avoid wasting the heat-adhesive resin and achieves effectiveheat-sealing using the least necessary amount of the heat-adhesiveresin.

Since the patterned heat-adhesive resin layer can be formed by aprinting means and the heat-adhesive resin is used in a dope, an optimumheat-adhesive resin can be selected out of a large variety of resins,and the patterned heat-adhesive resin layer can be formed by a desiredquantity of the heat-adhesive resin in a desired pattern.

The laminated sheet may additionally be provided with a barrier layerimpermeable to gases and moisture. The barrier layer may be a metalfoil, a thin layer of a metal, an inorganic oxide or a resin, such as apolyvinylidene chloride resin, a polyacrylonitrile resin or a saponifiedethylene-vinyl acetate copolymer.

The laminated sheet provided with such a barrier layer is impermeable tomoisture and gases.

When forming a laminated sheet provided with such a barrier layer, it ispreferable to sandwich the barrier layer between base film layers. Thebarrier layer thus sandwiched between the base films is protected fromdamage and is able to exercise its ability more effectively.

A metal foil, among those barrier layers, has the most barrier property.A battery case forming sheet having an enhanced barrier property can beprovided by sandwiching a metal foil between base film layers.

When the intermediate layer of a laminated sheet as a barrier layer is athin film layer of an inorganic oxide, or a resin, such as apolyvinylidene chloride resin, a polyacrylonitrile resin or a saponifiedethylene-vinyl acetate copolymer, all the component layers of thelaminated sheet are electrically nonconducting. Therefore, the terminalsare not shorted by the laminated sheet even if the terminals are baremetal foils. Thus, a battery case forming sheet excellent in bothbarrier property and safety can be provided.

The base film layer is a biaxially oriented polyethylene terephthalatefilm, a biaxially oriented nylon film or a biaxially orientedpolypropylene film.

Hereinafter, biaxially oriented polyethylene terephthalate films,biaxially oriented nylon films and biaxially oriented polypropylenefilms will be designated as PET films, ON films and OPP films,respectively.

Since the foregoing films are excellent in various kinds of strength andresistance, printability and processability including capability ofbeing laminated, and are relatively inexpensive, an economical batterycase forming sheet having a satisfactory ability can easily formed.

Materials and processes for fabricating battery case forming sheets inaccordance with the present invention will be described in connectionwith examples.

As mentioned above, a battery case forming sheet in accordance with thepresent invention is used for forming a battery case for containing thecomponent materials of a battery to form the battery. The sheet is alaminated sheet formed by laminating at least one base film layer and aheat-adhesive resin layer formed in a pattern. When necessary, a barrierlayer impermeable to moisture and gases is sandwiched between base filmlayers.

The base film layer may be, for example, a PET film, an ON film, an OPPfilm, a polyethylene naphthalate film, a polyimide film, a polycarbonatefilm or the like. When printability, processability including capabilityof being laminated and economical effect are taken into consideration inaddition to various kinds of strength and resistance, PET films, ONfilms and OPP films are particularly suitable materials.

PET films, in particular, have a low hygroscopic property, and areexcellent in rigidity, tensile strength, bending strength, impactstrength, abrasion resistance, heat resistance and water resistance.Thus, PET films have generally well balanced ability and only a fewdrawbacks.

Though relatively hygroscopic, ON films are excellent in flexibility,piercing strength, impact strength, bending strength and low-temperatureresistance.

OPP films are excellent in moisture resistance, water resistance,chemical resistance, tensile strength and bending strength, and areinexpensive, which is a significant advantage.

Preferably, the thicknesses of those base films are in the range of 5 to100 μm, more preferably, in the range of 12 to 30 μm.

The base film layer may be a single layer of any one of the foregoingfilms or may be a laminated layer formed by putting together differentkinds of those films.

As mentioned above, the barrier layer impermeable to moisture and gasesmay be a metal foil, a metal thin film, a thin film layer of aninorganic oxide, or a layer of a resin, such as a polyvinylidenechloride resin, a polyacrylonitrile resin, or a saponifiedethylene-vinyl acetate copolymer.

An aluminum foil and a copper foil are suitable metal foils. An aluminumfoil is the most preferable material for forming the metal foil layerbecause an aluminum foil is inexpensive, easy to process and easy tobond to a film.

A suitable thickness of the metal foil layer is in the range of 5 to 25μm.

For example, if a 9 μm thick aluminum foil is used for forming the metalfoil layer, the metal foil layer has a satisfactorily low water vaporpermeability less than 0.01 g/m²·24 hr or below at 40° C. and 90% RH.The moisture impermeability of the metal foil layer can easily beenhanced.

Metals suitable for forming the barrier layer are aluminum, tin, nickeland the like. Aluminum is preferable. Inorganic oxides suitable forforming the barrier layer are silicon dioxide, alumina, titanium oxide,iron oxides and magnesium oxide. Silicon dioxide and alumina areparticularly suitable.

These thin film layers having barrier property can be formed on aplastic base film in thicknesses in the range of 100 to 2000 Å by avacuum evaporation method, a sputtering method or the like.

The adhesion of the thin film layer to the surface of a base film can beenhanced by subjecting a surface of the base film on which one of thesethin film layers is to be formed to a well-known pretreatment, such as acorona discharge treatment or a plasma treatment, or coating the samewith a primer, such as a urethane resin.

If the barrier layer is a film of a resin, such as a polyvinylidenechloride resin, a polyacrylonitrile resin or a saponified ethylene-vinylacetate copolymer, the resin may be extruded by a dry lamination methodor an extrusion lamination method, for example, so as to be sandwichedbetween base films. A polyvinylidene chloride resin can be prepared in adope, and the dope of the polyvinylidene chloride resin can be spread ina film on a base film by a coating process. A saponified ethylene-vinylacetate copolymer can be formed in a film on a surface of a base film byan extrusion coating process.

A suitable thickness of the barrier layer of such a resin is in therange of 5 to 25 μm.

A heat-adhesive resin layer (sealant layer), i.e., the innermost layer,to be formed in a pattern can be formed by a printing means, such asgravure printing, flexographic printing or silk-screen printing.

A material for forming a heat-adhesive resin layer is prepared in asolution, an emulsion or a dispersion according to a processing means tobe employed.

The heat-adhesive resin must be heat-adhesive not only to itself, butalso to the surfaces of electrodes. Heat-adhesive resins meeting suchrequirements are, for example, ethylene-α-olefin copolymers,ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers,ethylene-methacrylate copolymers, ethylene-acrylic acid copolymers,ethylene-methacrylic acid copolymers, chlorinated polypropylene resins,urethanevinyl chloride-vinyl acetate copolymers. These resins may beused individually or in a blend.

A suitable resin may be selected according to the material of a surfaceon which the heat-adhesive resin layer is to be formed, the quality ofthe surfaces of the terminals and the like from those resins.

A suitable weight per unit area of the heat-adhesive resin layer is inthe range of 4 to 10 g/m² (solid content).

If the adhesion of the heat-adhesive resin layer to the base film isinsufficient, the surface of the base film may be pretreated by awell-known pretreatment, such as a corona discharge treatment, a plasmatreatment or a glow discharge treatment, or may be coated with a primer.

Examples of the seventh embodiment will be described hereinafter withreference to the drawings.

Examples shown in the drawings are illustrative and not limitative. Likeor corresponding parts are designated by the same reference charactersthroughout the drawings.

FIGS. 24 and 25 are typical sectional views of examples of battery caseforming sheets in accordance with the present invention.

FIG. 26 is a plan view of a battery case forming sheet provided with aheat-adhesive resin layer formed in a pattern on the innermost layerthereof and placed flat with its inner surface facing up.

FIG. 27 is a perspective view of an example of a battery case formed byprocessing the battery case forming sheet in accordance with the presentinvention shown in FIG. 26.

FIG. 28 is a front elevation of a battery fabricated by using thebattery case shown in FIG. 27.

Referring to FIG. 24, a battery case forming sheet 10 is formed byforming an heat-adhesive resin layer 3 in a pattern on one surface (aninner surface) of a base film layer (first base film layer) 1 a.

The base film layer 1 a may be a single film or a laminated film formedby a well-known method, such as a dry lamination method or an extrusionlamination method.

The following are representative examples of laminated films. Thelaminated films will be described below, in which pretreatment processesand adhesive layers employed therein will be omitted.

(1) PET film (25 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(2) OPP film (30 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(3) ON film (25 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(4) PET film (12 μm thick)/OPP film (20 μm thick)/Patternedheat-adhesive resin layer (5 μm thick) (Sealant layer)

(5) PET film (12 μm thick)/ON film (15 μm thick)/Patterned heat-adhesiveresin layer (5 μm thick) (Sealant layer)

A battery case forming sheet 10 shown in FIG. 25 has a laminatedconstruction formed by sequentially laminating a first base film layer 1a (the outermost layer), a barrier layer 12, a third base film layer 1 cand a patterned heat-adhesive resin layer formed on the inner surface ofthe third base film layer 1 c.

The base film layers 1 a and 1 c may be a single film or a laminatedfilm formed by laminating a plurality of films by a dry laminationmethod or an extrusion lamination method.

The following are representative examples of laminated films. Thelaminated films will be described below, in which pretreatment processesand adhesive layers employed therein will be omitted.

(1) PET film (12 μm thick)/Aluminum foil (9 μm thick)/PET film (12 μmthick)/Patterned heat-adhesive resin layer (5 μm thick) (Sealant layer)

(2) ON film (15 μm thick)/Aluminum foil (9 μm thick)/PET film (12 μmthick)/Patterned heat-adhesive resin layer (5 μm thick) (Sealant layer)

(3) OPP film (20 μm thick)/Aluminum foil (9 μm thick)/PET film (12 μmthick)/Patterned heat-adhesive resin layer (5 μm thick) (Sealant layer)

(4) PET film (12 μm thick)/Aluminum foil (9 μm thick)/OPP film (20 μmthick)/Patterned heat-adhesive resin layer (5 μm thick) (Sealant layer)

(5) PET film (12 μm thick)/Aluminum foil (9 μm thick)/ON film (15 μmthick)/Patterned heat-adhesive resin layer (5 μm thick) (Sealant layer)

(6) PET film (12 μm thick)/Silicon dioxide thin film layer (600 Åthick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(7) ON film (15 μm thick)/Silicon dioxide thin film layer (600 Åthick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(8) OPP film (20 μm thick)/Silicon dioxide thin film layer (600 Åthick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(9) PET film (12 μm thick)/Silicon dioxide thin film layer (600 Åthick)/OPP film (20 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(10) PET film (12 μm thick)/Silicon dioxide thin film layer (600 Åthick)/ON film (15 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(11) PET film (12 μm thick)/Polyvinylidene chloride thin film layer (3μm thick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5μm thick) (Sealant layer)

(12) ON film (15 μm thick)/Polyvinylidene chloride thin film layer (3 μmthick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(13) OPP film (20 μm thick)/Polyvinylidene chloride thin film layer (3μm thick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5μm thick) (Sealant layer)

(14) PET film (12 μm thick)/Polyvinylidene chloride thin film layer (3μm thick)/OPP film (20 μm thick)/Patterned heat-adhesive resin layer (5μm thick) (Sealant layer)

(15) PET film (12 μm thick)/Polyvinylidene chloride thin film layer (3μm thick)/ON film (15 μm thick)/Patterned heat-adhesive resin layer (5μm thick) (Sealant layer)

(16) PET film (12 μm thick)/ON film (15 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(17) ON film (15 μm thick)/OPP film (20 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(18) PET film (12 μm thick)/OPP film (20 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Patterned heat-adhesive resin layer (5 μmthick) (Sealant layer)

(19) PET film (12 μm thick)/ON film (15 μm thick)/Saponifiedethylene-vinyl acetate copolymer layer (20 μm thick)/PET film (12 μmthick)/Patterned heat-adhesive resin layer (5 μm thick) (Sealant layer)

(20) ON film (15 μm thick)/PET film (12 μm thick)/Saponifiedethylene-vinyl acetate copolymer layer (20 μm thick)/PET film (12 μmthick)/Patterned heat-adhesive resin layer (5 μm thick) (Sealant layer)

(21) PET film (12 μm thick)/OPP film (20 μm thick)/Polyacrylonitrileresin film (20 μm thick)/PET film (12 μm thick)/Patterned heat-adhesiveresin layer (5 μm thick) (Sealant layer)

FIG. 26 is a plan view of a battery case forming sheet provided with aheat-adhesive resin layer formed in a pattern on the innermost layerthereof and placed flat with its inner surface facing up.

Referring to FIG. 26, a battery case forming sheet 10 is provided with aheat-adhesive resin layer 3 formed in a pattern having parts extendingalong the edges thereof.

This battery case forming sheet 10 is folded in two leaves along afolding line 16 dividing the battery case forming sheet 10 into twoequal halves so that the corresponding parts of the heat-adhesive resinlayer 3 are in contact with each other, and the parts of theheat-adhesive resin layer 3 formed in the opposite side edge parts ofthe folded battery case forming sheet 10 are heat-sealed to form abattery case 51 having on open end as shown in FIG. 27.

A battery case 51 having the shape of a pouch having one open end can beformed by putting together two battery case forming sheets 10 in asuperposed structure so that the corresponding parts of theheat-adhesive resin layers 3 are in contact with each other, andheat-sealing three edge parts of the superposed structure.

The battery case 51 shown in FIG. 27 has a bottom part formed by foldingthe battery case forming sheet, opposite heat-sealed side edge parts 17,and an open upper end 18.

This battery case 51 can be formed by folding the battery case formingsheet 10 in two leaves along the folding line 16 dividing the batterycase forming sheet 10 into two equal halves so that the correspondingparts of the heat-adhesive resin layer 3 are in contact with each other,and heat-sealing the parts of the heat-adhesive resin layer 3 formed inthe opposite side edge parts of the folded battery case forming sheet 10so as to form heat-sealed edge parts 17. Since parts of a predeterminedwidth of the heat-adhesive resin layer 3 are formed on the innersurfaces of the upper end edge parts of the open upper end 18 of thebattery case 51, the component materials of a battery 50 a can beassembled in the battery case 51, tabs 59 and 60 are extended from theinside through the open upper end 18 so as to extend outside the batterycase 51, and then the open upper end 18 can be heat-sealed.

A polymer battery packet 50 shown in FIG. 28 is fabricated by assemblingthe component materials of a battery 50 a in the battery case 51 shownin FIG. 27, extending tabs 59 and 60 from the inside through the openupper end 18 so as to extend outside the battery case 51, andheat-sealing an upper heat-sealed edge part 17 with the tabs 59 and 60hermetically sandwiched between the upper end edge parts of the batterycase 51.

As is apparent form the foregoing description, the present inventionprovides lightweight, thin, flexible, laminated sheet excellent invarious kinds of mechanical strength, resistance to detrimental effects,and impermeability to moisture and gases. Since the laminated sheet isprovided with the heat-sealing resin layer formed in a pattern on itsinner surfaces, parts of the heat-adhesive resin layer are formed onlyon necessary parts of the laminated sheet, and a battery case having theshape of a pouch can effectively be formed without wasting materials.The battery case forming sheet for fabricating a battery by assemblingthe component materials of a battery in a battery case, extendingterminals from the inside through the open upper end so as to extendoutside the battery case, and heat-sealing an open end edge part of thebattery case through which the terminals are extend can efficiently beproduced.

Eighth Embodiment

An eighth embodiment according to the present invention will bedescribed with reference to FIGS. 29 to 33. A battery case in the eighthembodiment is substantially the same as that in the first embodiment,except that the battery case in the eighth embodiment has at least apart formed of a laminated film formed by sandwiching an aluminum foillayer, i.e., an intermediate layer, between synthetic resin layers, anda pressure relieving part provided with incisions formed by irradiationwith a laser beam is formed in at least one of the surfaces of thelaminated film.

According to the present invention, the term, “pressure relieving part”(burst-proof structure) designates a structure formed by melting andevaporating linear portions of some or all of the synthetic resin layerson one side of the aluminum foil layer, i.e., the intermediate layer, byirradiating the same with a laser beam.

Furthermore, the term, “burst-proof structure” designates a structurehaving a reduced breaking strength, provided with cuts formed in apredetermined shape in the laminated film and capable of making thelaminated film break when a pressure in a predetermined range is appliedthereto before the same bursts.

A battery case forming laminated film of the foregoing construction isprovided with an aluminum foil layer, i.e., an intermediate layer,having an excellent barrier property not permitting moisture and gasesto pass through, and a burst-proof structure having a reduced breakingstrength formed by forming cuts at least in a layer on one side of theintermediate layer. The aluminum foil layer will not be damaged when thebattery case forming laminated film is processed and is able to maintainits excellent barrier property. The burst-proof structure breaks whenpressure in a battery case formed by shaping the battery case forminglaminated film increases to a predetermined level to relieve thepressure in the battery case, so that the battery case will not burst.Thus, the battery case is excellent in safety.

The breaking strength of the burst-proof structure, i.e., the pressurerelieving part, is in the range of 5 to 10 kg/cm².

Since the burst strength of the battery case is adjusted to a properlyvalue by the burst-proof structure, the battery case will not burst evenif pressure in the battery case increases abnormally because theburst-proof structure breaks before the battery case bursts, whichenhances the safety of the battery case.

If the breaking strength of the burst-proof structure is less than 5kg/cm², the breaking strength of the laminated film is excessively lowand the laminated film may possibly be damaged during the use of thebattery. If the breaking strength of the burst-proof structure is above10 kg/cm², the battery case may possible explode to cause danger and theeffect of the burst-proof structure is insufficient.

The pressure relieving part may be provided with linear incisionsintersecting each other or meeting on a point.

Such linear cuts facilitate the adjustment of the lower limit of thebreaking strength of the pressure relieving part, reduce the deviationof the breaking strength from a desired value and form a stableburst-proof structure.

The laminated film may be provided with pressure relieving parts formedin both the surfaces thereof so as to coincide with each other.

Such pressure relieving parts formed in both the surfaces of thelaminated film enable setting the breaking strength of the pressurerelieving part, i.e., the burst-proof structure, at a further reducedvalue, reduces the deviation of the breaking strength from a desiredvalue and ensures the formation of a further safe burst-proof structure.

The battery case is a pouch formed by processing the laminated sheet andheat-sealing the peripheral parts of the pouch, and is provided with apressure relieving part in a peripheral part thereof.

The battery case of such a construction can be formed of only thelaminated film. Therefore, the battery case is thin, light andinexpensive. Since the battery case is provided with the pressurerelieving part in its peripheral part, a stress can easily be induced inthe pressure relieving part by the pressure in the battery case.Therefore, the reliability of the burst-proof structure is furtherenhanced.

Examples of materials of battery cases provided with a burst-proofstructure in accordance with the present invention and methods offabricating such battery cases will be described below.

As mentioned above, a battery case provided with a burst-proof structurein accordance with the present invention is used for fabricating abattery by assembling the component materials of the battery in thebattery case. The battery case has at least a part formed of a laminatedfilm formed by sandwiching an aluminum foil layer, i.e., an intermediatelayer, between synthetic resin layers, and a pressure relieving part,i.e., a burst-proof structure, provided with cuts formed by irradiationwith a laser beam is formed in at least one of the surfaces of thelaminated film.

Although it is preferable to form a battery case only of the laminatedfilm by shaping the laminated film provided with the burst-proofstructure in a pouch, a battery case may be formed by attaching thelaminated sheet provided with the burst-proof structure as a wall memberto a frame formed by molding a plastic material.

The laminated film is formed by laminating synthetic resin layersserving as outer and inner surfaces, respectively, of a battery case tothe opposite surfaces of an aluminum foil layer serving as a barrierlayer, a laser beam intercepting layer and an intermediate layer.

The outer synthetic resin layer has various kinds of strength andresistance, and a pressure relieving part provided with cuts is to beformed therein by irradiation with a laser beam. Therefore, the outersynthetic resin layer must absorb the laser beam, and must generateheat, melt and evaporate upon the absorption of the laser beam. It ispreferable that the outer synthetic resin layer is printable andprocessable for lamination and the like. Suitable materials for formingthe outer synthetic resin layer are, for example, biaxially orientedpolyethylene terephthalate resin films, biaxially oriented nylon resinfilms, biaxially oriented polyethylene naphthalate resin films andbiaxially oriented polypropylene resin films. The outer synthetic resinlayer may be one of those films or may be a laminated film formed bylaminating some of those films.

Hereinafter, biaxially oriented polyethylene terephthalate films,biaxially oriented nylon films and biaxially oriented polypropylenefilms will be designated as PET films, ON films and OPP films,respectively.

PET films, in particular, have a low hygroscopic property, and areexcellent in rigidity, tensile strength, bending strength, impactstrength, abrasion resistance, heat resistance and water resistance.Since PET films have generally well balanced ability and are relativelyinexpensive and economically advantageous, PET films are suitablematerial.

Though relatively hygroscopic as compared with PET films, ON films areexcellent in flexibility, piercing strength, impact strength, bendingstrength and low-temperature resistance. ON films are suitable when suchfunctions are important.

OPP films are excellent in moisture resistance, water resistance,chemical resistance, tensile strength and bending strength, and areinexpensive, which is a significant advantage.

The outer synthetic resin layer can be formed by laminating theforegoing film by dry lamination or the like to the aluminum foilserving as an intermediate layer.

Preferably, the thicknesses of the plastic film, i.e., the outersynthetic resin layer, is in the range of 8 to 80 μm, more preferably,in the range of 12 to 30 μm.

The inner synthetic resin layer of the laminated film must be capable ofreinforcing the laminated film, of protecting the intermediate aluminumfoil layer, of being processed with a laser beam to form a pressurerelieving part, and of being heat-adhesive not only to itself, but alsoto the surfaces of terminals to enable the laminated film to be shapedin a pouch and to enable and open end of the pouch to be satisfactorilyheat-sealed.

Since it is difficult to form the inner synthetic resin layer meetingsuch requirements of a single resin layer (film), it is preferable toform the inner synthetic resin layer of a laminated sheet consisting ofat least two layers.

For example, the inner synthetic resin layer may be formed of atwo-layer structure consisting of a plastic film layer similar to thatforming the outer synthetic resin layer, and a heat-adhesive resin layer(sealant layer). The inner synthetic resin layer may be laminated to theinner surface of the intermediate aluminum foil layer so as to serve asthe innermost layer.

Suitable materials for forming the heat-adhesive resin layer arepolyethylene resins, ethylene-α-olefin copolymers, ethylene-vinylacetate copolymers, ethylene-acrylate copolymers, ethylene-methacrylatecopolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acidcopolymers, acid-denatured polyolefin resins and ionomers. Thesematerials may be used individually or in a blend.

A suitable resin may be selected according to the quality of thesurfaces of the terminals (coated or not coated) from those resins.

The plastic film for forming the inner synthetic resin layer need not bevery thick; a suitable thickness of the plastic film is in the range ofabout 8 to about 30 μm.

Preferably, the innermost heat-adhesive resin layer is in the range of15 to 100 μm, more preferably, in the range of 30 to 80 μm.

Preferably, the thickness of the intermediate aluminum foil layer is inthe range of 5 to 25 μm, more preferably, in the range of 7 to 25 μm.

An aluminum foil layer of a thickness less than 5 μm is undesirablebecause many pinholes are liable to be formed in such a thin aluminumfoil layer to reduce the barrier property not to permit moisture andgases to pass through of the aluminum foil layer. An aluminum foil layerof a thickness above 25 μm is undesirable because such a thick aluminumfoil layer has an excessively high barrier property and provides thepressure relieving part with an excessively high breaking strength.

For example, if a 9 μm thick aluminum foil is used for forming theintermediate layer, the intermediate layer has a satisfactorily lowwater vapor permeability less than 0.01 g/m²·24 hr or below at 40° C.and 90% RH. The moisture impermeability of the intermediate layer caneasily be enhanced.

According to the present invention, a part of the laminated film formedof the foregoing materials is irradiated with a laser beam to form apressure relieving part provided with cuts by melting and evaporatinglinear portions of some or all of the synthetic resin layers on theopposite sides of the aluminum foil layer. The pressure relieving partserves as a burst-proof structure of a reduced breaking strength in therange of 5 to 10 kg/cm².

The cuts for forming the pressure relieving part can be formed by awell-known laser beam projecting means. A laser beam projecting meansprovided with a carbon dioxide gas laser is particularly suitable.

A carbon dioxide gas laser emits Laser light of 10.6 m in wavelength.The PET films, ON films and OPP films mentioned above as materialssuitable for forming the synthetic resin layers of the laminated filmgenerate heat upon the absorption of the laser light of such awavelength emitted by a carbon dioxide gas laser, and hence a pressurerelieving part provided with cuts can easily be formed in those films.

Low-density polyethylene resins generally used as heat-adhesive resinsabsorb a laser beam of this wavelength scarcely and transmit the same.Therefore, low-density polyethylene resins do not generate heat whenirradiated with a laser beam of this wavelength and hence cannot beprocessed with the laser beam. However, a low-density polyethylene resinfilm can be used in combination with some one of the PET films, the ONfilms and the OPP films and cuts can be formed therein because the PETfilms, ON films and OPP films generate heat when irradiated with thelaser beam, and the low-density polyethylene resin film is melted by theheat.

Accordingly, if the inner synthetic resin layer of the laminated film isa two-layer laminated sheet consisting of a PET film, an ON film or anOPP film, and a heat-adhesive resin layer of a low-density polyethyleneresin, a pressure relieving part provided with a pattern of linear cutscan be formed by removing, for example, parts of both the two componentlayers of the inner synthetic resin layer in the pattern of a pressurerelieving part provided with a pattern of linear hollows formed byremoving only parts of the PET, the ON or the OPP film, temporarilymelting parts of the low-density polyethylene resin layer and allowingthe molten parts of the low-density polyethylene resin layer to repairits initial shape by properly determining the respective thicknesses ofthe two component layers of the inner synthetic resin layer and properlyadjusting conditions for irradiation with a laser beam.

The present invention will more specifically be described with referenceto the accompanying drawings. The present invention is not limited inits practical application to the examples shown in the accompanyingdrawings.

FIG. 29 is a typical sectional view of a laminated film for forming abattery case provided with a burst-proof structure in accordance withthe present invention.

FIGS. 30(a), 30(b), 30(c) and 30(d) are representative patterns oflinear cuts formed in laminated films by irradiation with a laser beam.

FIGS. 31(a) and 31(b) are typical sectional views of examples ofpressure relieving parts formed in laminated films.

FIG. 32 is a development of a battery case provided with a burst-proofstructure in accordance with the present invention and having the shapea pouch having three sides sealed by heat-sealing.

FIG. 33 is a front view of a battery employing the battery case shown ina development in FIG. 32.

Referring to FIG. 29, a laminated sheet 10 has an aluminum foil layer(metal foil layer) 2, i.e., an intermediate layer, an outer syntheticresin layer (first base film layer) 1 a laminated to the outer surface(upper surface as viewed in FIG. 29) of the aluminum foil layer 2, andan inner synthetic resin layer (third base film layer) 1 c laminated tothe inner surface (lower surface as viewed in FIG. 29) of the aluminumfoil layer 2.

Concretely, the outer synthetic resin layer 1 a is a PET film, an ONfilm or an OPP film, and the inner synthetic resin layer 1 c is a PETfilm, an ON film or an OPP film. A heat-adhesive resin layer 3, aninnermost layer, is laminated to the inner synthetic resin layer 1 c.

Each of the outer synthetic resin layer 1 a and the inner syntheticresin layer 1 c may be one of a PET film, an ON film and an OPP film ormay be a laminated film consisting of one or some of a PET film, an ONfilm and an OPP film, and a film of another kind.

The innermost heat-adhesive resin layer 3 may be of either asingle-layer construction or a multilayer construction.

Although it is preferable to laminate the first base film layer 1 a andthe third base film layer 1 c, i.e., some of PET films, ON films and OPPfilms, to the intermediate aluminum foil layer 2 by a well-known drylamination method using an adhesive, the same may be laminated to thealuminum foil layer 2 by an extrusion lamination method using aheat-adhesive resin.

Although it is easy and simple to form the innermost heat-adhesive resinlayer 3 by an extrusion coating method, the heat-adhesive resin layer 3may be formed by laminating a heat-adhesive resin film to the third basefilm layer 1 c by a dry lamination method or an extrusion laminationmethod.

The following are representative examples of the laminate films. In thefollowing description, pretreatment processes and adhesive layersemployed in forming the laminated films are omitted.

(1) PET film (16 μm thick)/Aluminum foil (9 μm thick)/PET film (12 μmthick)/Heat-adhesive resin layer (40 μm thick) (Sealant layer)

(2) ON film (15 μm thick)/Aluminum foil (9 μm thick)/PET film (12 μmthick)/Heat-adhesive resin layer (40 μm thick) (Sealant layer)

(3) OPP film (20 μm thick)/Aluminum foil (9 μm thick)/PET film (12 μmthick)/Heat-adhesive resin layer (40 μm thick) (Sealant layer)

(4) PET film (16 μm thick)/Aluminum foil (9 μm thick)/OPP film (20 μmthick)/Heat-adhesive resin layer (40 μm thick) (Sealant layer)

(5) PET film (16 μm thick)/Aluminum foil (9 μm thick)/ON film (15 μmthick)/Heat-adhesive resin layer (40 μm thick) (Sealant layer)

(6) ON film (15 μm thick)/PET film (12 μm thick)/aluminum foil (9 μmthick)/PET film (12 μm thick)/Heat-adhesive resin layer (40 μm thick)(Sealant layer)

(7) PET film (12 μm thick)/ON film (15 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Heat-adhesive resin layer (40 μm thick)(Sealant layer)

(8) PET film (12 μm thick)/OPP film (15 μm thick)/Aluminum foil (9 μmthick)/PET film (12 μm thick)/Heat-adhesive resin layer (40 μm thick)(Sealant layer)

According to the present invention, cuts are formed in a pattern byirradiating the foregoing laminated film with a laser beam to form aburst-proof structure having a breaking strength in the range of 5 to 10kg/cm².

There is not any particular restrictions on the pattern of the cuts, andthe cuts may be formed in an optional pattern, taking into considerationthe qualities and the thicknesses of the synthetic resin layers of thelaminated film.

Patterns of cuts shown in FIGS. 30(a) to 30(d) are suitable for forminga pressure relieving part 20.

All the patterns for forming the pressure relieving part 20 shown inFIGS. 30(a) to 30(d) are formed of cuts extending radially from acentral point.

The pattern shown in FIG. 30(a) is formed by radially extending threestraight cuts from a central point at angular intervals of 120°. Thepattern shown in FIG. 30(b) is formed by radially extending fourstraight cuts from a central point at angular intervals of 90°. Thepattern shown in FIG. 30(c) is formed by radially extending six straightcuts from a central point at angular intervals of 60°. The pattern shownin FIG. 30(a) is formed by radially extending eight straight cuts from acentral point at angular intervals of 45°.

The pressure relieving part 20 having a pattern of a greater number ofcuts has a lower breaking strength. Suitable one of the pressurerelieving parts 20 shown in FIGS. 30(a) to 30(d) is selected, takinginto consideration the construction of the laminated film sheet.Although there is not any particular restrictions on the size of thepattern, a suitable length of the straight cuts is in the range of about10 to about 15 mm, and hence a suitable diameter of a circlecircumscribed about the pattern is in the range of about 20 to about 30mm.

Although the pressure relieving part 20 having such a pattern of cutsmay be formed only on one side of the laminated film, the breakingstrength of the laminated film can further be reduced when the pressurerelieving parts 20 are formed in both the synthetic resin layers so asto coincide with each other.

FIGS. 31(a) and 31(b) are typical sectional views of pressure relievingparts 20 formed in the opposite synthetic resin layers, respectively, oflaminated films each formed by laminating a PET film layer (theoutermost layer) 1 a, an aluminum foil layer 2, a PET film layer 1 c,and a polyolefin resin layer (sealant layer) 3.

The inner synthetic resin layer 1 c assumes either a shape shown in FIG.31(a) or a shape shown in FIG. 31(b) when the innermost polyolefin resinlayer 3 is a resin layer which does not absorb laser light, such as alow-density polyethylene resin, depending on its thickness andconditions for irradiation with a laser beam.

The pressure relieving part 20 shown in FIG. 31(a) is formed by removinglinear parts of the synthetic resin layers 1 a and 1 c and the sealantlayer 3. If the polyolefin resin layer is as thick as 40 μm or above andthe energy of the laser beam is adjusted to a certain fixed level,linear parts of both the inner synthetic resin layer 1 c, i.e., the PETfilm layer, and the polyolefin resin layer are melted and torn, and thesealant layer 3, i.e., the polyolefin resin layer, is allowed to repairits initial shape to form a pattern of linear hollows only in the innersynthetic resin layer 1 c as shown in FIG. 31(b).

FIG. 32 is a development of a battery case 51 provided with aburst-proof structure in accordance with the present invention andhaving the shape a pouch having three sides sealed by heat-sealing.

The battery case shown in this development is formed by shaping thelaminated sheet 10 shown in FIG. 29. This laminated sheet 10 has arectangular shape of a predetermined dimensions, is provided withpressure relieving parts 20 each having four straight cuts radiallyextending from a central point at angular intervals of 90° in theopposite surfaces thereof so as to correspond to each other at aposition near a folding line 16 dividing the laminated sheet 10 into twoequal halves, and is provided with side sealing parts 17 a, 17 b, 17 cand 17 d in its side edge parts, and end sealing parts 18 a and 18 b inits end edge parts.

A battery case having the shape of a rectangular pouch and an open endhaving the end sealing parts 18 a and 18 b can be formed by folding thelaminated sheet 10 in two leaves along the folding line 16 so that theheat-adhesive layers come into contact with each other, and bonding theside sealing parts 17 a and 17 b together and the side sealing parts 17c and 17 d together by heat-sealing.

A polymer battery packet 50 provided with a burst-proof structure havingthe pressure relieving part 20 as shown in FIG. 33 is fabricated byassembling the component materials of the battery in the battery case 51having the shape of a pouch, extending tabs 59 and 60 from the insidethrough the open upper end 18 so as to extend outside the battery case51, and sealing an open upper end by bonding together the heat-adhesiveresin layers by heat-sealing with the tabs 59 and 60 hermeticallysandwiched between the upper end edge parts of the battery case 51.

FIG. 33 is a front elevation of a battery packet 50 employing thebattery case 51 formed by shaping the laminated sheet 10 shown in FIG.32 in a development. The battery case 51 is formed by folding thelaminated sheet 10 in two leaves, and bonding the side sealing parts 17a and 17 b together and the side sealing parts 17 c and 17 d together byheat-sealing. The component materials of the battery are put in thebattery case 51 through the open upper end, tabs 59 and 60 are extendedfrom the inside of the battery case 51 through the open upper end so asto extend outside the battery case 51, and the open upper end is sealedby bonding together the end sealing parts 18 a and 18 b by heat-sealing.The battery case 51 is provided in its bottom part with a burst-proofstructure having the pressure relieving parts 20.

As is apparent from the foregoing description, according to the presentinvention, the battery case is formed by processing the laminated filmformed by sandwiching the intermediate aluminum foil layer between thesynthetic resin layers, is light, thin, flexible, excellent in variousstrength and resistance, barrier property not permitting moisture andgases to pass through and heat-sealability, is provided with theburst-proof structure which relieves the pressure in the battery case ifthe pressure increases beyond a predetermined upper limit due to heatgeneration caused by the misapplication of the battery packet, andcapable of securing high safety and of being efficiently produced.

Ninth Embodiment

A battery case forming sheet in a ninth embodiment according to thepresent invention will be described with reference to FIGS. 34 to 36.The battery case forming sheet in the ninth embodiment is a polymerbattery case forming sheet. The battery case forming sheet is alaminated sheet of a construction: first base layer/metal foillayer/adhesive resin layer/third base layer/heat-adhesiveres in layer.The metal foil layer and the third base layer, and the third base layerand the heat-adhesive resin layer are laminated by a sandwich laminationmethod or an extrusion coating method. The adhesive resin layer and/orthe heat-adhesive resin layer is formed of an acid-denatured polyolefinresin. The acid-denatured polyolefin resin has a melting point of 100°C. or above. The battery case forming sheet in the ninth embodiment issubstantially the same in other respects as that in the firstembodiment.

FIG. 34 is a typical sectional view of a battery case forming sheet inthe ninth embodiment, FIG. 35 is a typical sectional view of anotherbattery case forming sheet in the ninth embodiment, FIG. 36(a) is aperspective view of a polymer battery packet in accordance with thepresent invention, and FIG. 36(b) is a sectional view taken on line X—Xin FIG. 36(a).

Referring to FIG. 36, the polymer battery packet in accordance with thepresent invention has a battery 50 a, tabs 59 and 60, and a case 51sealing the battery 50 a and the tabs 59 and 60 therein. The tabs 59 and60 are extended from the inside of the case 51 so as to extend outsidethe case 51, and parts of the tabs 59 and 60 are attached adhesively toan inner layer of the case 51 in a sealed part 17 of the case 51.

Battery case forming sheets of the foregoing construction are puttogether with their heat-adhesive resin layers in contact with eachother, peripheral edge parts of the battery case forming sheets arebonded together by heat-sealing to form a battery case 51 having theshape of a pouch and an open end part. The component materials of abattery 50 a including positive and negative electrodes and electrolyteare put in the battery case 51, tabs 59 and 60 are extended from theinside of the battery case 51 so as to extend outside the battery case51, and the open upper end is sealed by bonding together theheat-adhesive resin layers, and the heat-adhesive resin layers and thetabs 59 and 60 together by heat-sealing to complete a battery packet.

Therefore, the heat-adhesive resin layers are formed of a heat-adhesiveresin heat-adhesive not only to itself, but also to the tabs 59 and 60made of a conductive material, such as copper foil or an aluminum foil.

The battery case forming sheet for a polymer battery packet is alaminated sheet consisting of an outer base layer, a metal foil layer,i.e., a barrier layer, and a heat-adhesive resin layer. Generally, athird base layer is interposed between the metal foil layer and theheat-adhesive resin layer to prevent the development of pinholes in themetal foil layer and the breakage of the same due to bending or piercingof the metal foil layer. In the battery case forming sheet of such aconstruction, the intermediate metal foil layer provides an excellentbarrier property not permitting moisture and gases to pass through, thebase layer formed on one surface of the metal foil layer, and the baselayer or the heat-adhesive resin layer formed on the other surface ofthe metal foil layer protect the metal foil layer, so that developmentof fissures and pinholes can be prevented to maintain satisfactorybarrier property.

The base layer formed on the outer or the inner surface of the metalfoil layer protects the metal foil layer and, at the same time, providesthe sheet with strength and abilities. The innermost heat-adhesive resinlayer provides the sheet with heat-sealability.

Since the metal foil layer is sandwiched between at least thenonconducting first and the nonconducting third base layer, the batterycase forming sheet functions as a nonconducting sheet.

It was found through examinations that the battery sealed in a batterycase formed by shaping the battery case forming sheet can be protectedfrom external and internal shocks or piercing actions when the batterycase forming sheet is a laminated sheet formed by sandwiching thebarrier layer between the outer first base layer and the inner thirdbase layer.

The case having the shape of a pouch is formed by bonding togetherlaminated sheets by heat-sealing. Therefore, the innermost layer of eachlaminated sheet is a heat-adhesive resin layer. The heat-adhesive resinlayer is formed of an acid-denatured polyolefin resin heat-adhesive to ametal forming terminals T.

The acid-denatured polyolefin resin forming the heat-adhesive resinlayer is satisfactorily adhesive not only to itself, but also to ametal, such as copper or aluminum. Therefore, the open end of thebattery case can be heat-sealed.

Sometimes, a laminated sheet formed by a generally known dry laminationmethod delaminates while a case formed by processing the same is in usedue to deterioration by aging during storage. It was found through theanalysis of causes of delamination that an adhesive used for drylamination is dissolved in the electrolyte of the polymer battery duringlong storage because the electrolyte is an organic carbonate solvent andthe adhesive is soluble in an organic solvent. Thus, the electrolyte,i.e., a component of the battery, permeates the resin layer of the caseand reaches the interface between the resin layer and the adhesive layerin a long time, dissolves the adhesive to cause the final delaminationof the laminated sheet.

Sometimes the battery packet is used or left in a high-temperatureenvironment. It is possible, if the case is not heat-resistant, that theheat-sealed parts of the case are unsealed and the electrolyte leakswhen the case is exposed to high temperatures. For example, the batterypacket is required to withstand a test called a dashboard test in whichan electronic device provided with the battery packet is kept in avehicle. More specifically, it is required that any liquid does not leakfrom the battery packet when the battery packet is kept in anenvironment of 100° C. for five hours.

It was found through the studies of the construction of variouslaminated sheets and the materials of laminated sheets that theforegoing problems can be solved and the requisite conditions of a casefor a polymer battery can be satisfied by a laminated sheet of thefollowing construction, and the present invention has been made on thebasis of findings acquired by the studies.

The first base layer, i.e., a base member of the laminated sheet, mustbe sufficiently strong and satisfactorily processable for printing,lamination and the like when fabricating a laminated sheet, and musthave various abilities including abrasion resistance and the likenecessary for serving as the surface layer of a battery packet.

Cases of batteries including polymer batteries must have a barrierproperty not permitting moisture and gases to pass through. The presentinvention employs a metal foil as a barrier layer. A third base layer isbonded to the inner surface of the metal foil to protect the barrierlayer and to reinforce a battery case. An innermost layer is formed of aheat-adhesive resin. Thus, a laminated sheet in accordance with thepresent invention comprises, as indispensable components, a metal foilserving as a barrier layer, a base layer and a heat-adhesive resinlayer.

The metal foil layer and the third base layer are bonded together bysandwich lamination using an adhesive resin. In this laminated sheet,the heat-adhesive resin layer is formed of an acid-denatured polyolefinresin capable of withstanding temperatures of 100° C. or above.

A polymer battery case 51 in accordance with the present invention willbe described hereinafter.

According to the present invention, adhesive layers of solvent-solubleadhesives dissolvable in an organic solvent are not used in forming aninner laminated sheet on the inner side of the barrier layer, the layersof the inner laminated sheet are laminated by a sandwich laminationmethod using an adhesive resin, and the innermost heat-adhesive resinlayer of the inner laminated sheet is formed by an extrusion coatingmethod.

The component layers of an outer laminated sheet on the outer side ofthe metal foil layer may be laminated by the foregoing dry laminationmethod.

Since the inner laminated sheet on the inner side of the metal foillayer is built without using any solvent-soluble adhesive layer, thereis no possibility that the inner laminated sheet is delaminated by tothe penetration of the electrolyte into the bonding interface and thedissolving of the adhesive layer by the electrolyte.

The individual layers of the laminated sheet forming a battery caseforming sheet in accordance with the present invention for forming apolymer battery will be described hereinafter.

As mentioned above, a battery case forming sheet in accordance with thepresent invention has a metal foil layer serving as an intermediatelayer and having a barrier property not permitting moisture and gassesto pass through, first, third and additional third base layers excellentin various kinds of strength and resistance are arranged property on theouter and the inner side of the metal foil layer, and a heat-adhesiveresin layer is formed as an innermost layer.

Suitable materials for forming the intermediate metal foil layerproviding a gas-barrier property is an aluminum foil, a copper foil orthe like. An aluminum foil is the most preferable material for formingthe metal foil layer because an aluminum foil is inexpensive, easy toprocess and easy to bond to a film. A suitable thickness of the metalfoil layer is in the range of 5 to 25 μm.

Suitable materials for forming the base layer are, for example,biaxially oriented polyethylene terephthalate resin films (herein afterreferred to as “PET films” or “PETS”), biaxially oriented nylon resinfilms (hereinafter referred to as “ON films” or “ON”), biaxiallyoriented polypropylene resin films (hereinafter designated as, “OPPfilms” or “OPP”). polyethylene naphthalate resin films, polyimide resinfilms, polycarbonate resin films and the like. In view of abilitiesincluding durability, processability and economical effect, PET filmsand ON films are particularly suitable.

Although PET films and ON films are not particularly different inproperties from each other, PET films have low hygroscopic property andare excellent in rigidity, abrasion resistance and heat resistance, ONfilms have relatively high hygroscopic property and are excellent inflexibility, piercing strength, bending strength and low-temperatureresistance.

Preferably, the thickness of the base films is in the range of 5 to 100μm, more preferably, 12 to 30 μm.

As mentioned above, it is preferable that the heat-adhesive resin layer,i.e., the innermost layer, is heat-adhesive not only to itself, but alsoto a metal forming terminals, has a low hygroscopic or moistureabsorbing property to suppress the penetration of moisture into theelectrolyte, and is stable and unsusceptible to the swelling andcorrosive actions of the electrolyte.

In view of such desirable conditions, suitable materials for forming theheat-adhesive resin layer are, for example, ethylene-vinyl acetatecopolymers, ethylene-acrylate copolymers, ethylene-methacrylatecopolymers and polyolefin resins prepared by blending a polyethyleneresin or a polypropylene resin, and one or some of those copolymers.Particularly preferable heat-adhesive resins are, for example,ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers,and resins produced by modifying polyethylene resins, polypropyleneresins, and resins produced by graft copolymerization includingethylene-propylene copolymers, ethylene-α-olefin copolymers,propylene-α-olefin copolymers, ethylene-vinyl acetate copolymers,ethylene-acrylate copolymers, ethylene-methacrylate copolymers andterpolymers of those resins by some of unsaturated carboxylic acids andanhydrides of unsaturated carboxylic acids, such as acrylic acid,methacrylic acid, maleic acid, maleic anhydride, citraconic anhydride,itaconic acid and itaconic anhydride.

Some resins having a melting point of 100° C. or above among thoseresins are used.to form battery cases having excellent heat resistance.If the melting point of the acid-denatured polyolefin resin forming theheat-adhesive resin layer is below 100° C., there is the possibilitythat the sealed parts of the battery case are unsealed and theelectrolyte leaks when the battery packet is exposed to hightemperatures.

Battery case are unsealed and the electrolyte leaks when a batterypacket formed by building a battery in the battery case is exposed tohigh temperatures.

Preferable acid content of the acid-denatured polyolefin resins is inthe range of 0.01 to 10% by weight. The heat-adhesion of the resin to ametal is insufficient if the acid content is less than 0.01% by weight,and the film forming performance of the resin is inferior if the acidcontent is higher than 10% by weight.

A suitable thickness of the heat-adhesive resin layer is in the range of10 to 100 μm.

The component layers may be laminated on the inner side of the metalfoil layer by a known sandwich lamination method which extrudes a moltenadhesive resin between two layers to be laminated and compresses thelayers and a layer of the heat-adhesive resin sandwiched between thelayers.

The foregoing acid-denatured polyolefin resin is used as the adhesiveresin.

The innermost heat-adhesive resin layer is formed by extruding a moltenacid-denatured polyolefin resin directly on the third base layer. Whenforming the laminated sheet in accordance with the present invention asa sheet for forming a polymer battery case, whereas the laminated layeron the inner side of the metal foil layer is formed by a dry laminationmethod using an acid-denatured polyolefin resin as the adhesive resininstead of by a dry lamination method using an organic adhesive, thelaminated layer on the outer side of the metal foil layer may be formedby a dry lamination method.

The present invention will more concretely be described with referenceto the accompanying drawings.

Examples shown in the drawings are illustrative and not limitative. Likeor corresponding parts are designated by the same reference charactersthroughout the drawings.

FIGS. 34 and 35 are typical sectional views of battery case formingsheets in examples in accordance with the present invention for formingthe battery case 51.

Referring to FIG. 34, a battery case forming sheet 10 is formed bysequentially laminating a first base layer (first base film layer) 1 a,an adhesive resin layer 5, a metal foil layer 2, an adhesive resin layer4, a third base layer (third base film layer) 1 c and a heat-adhesiveresin layer 3.

The first base layer 1 a is a PET film or an ON film. The metal foillayer 2 is, for example, an aluminum foil. Each of the adhesive resinlayers and the heat-adhesive resin layer 3 is formed of anacid-denatured polyolefin resin having an acid content in the range of0.01 to 10% by weight.

The first base layer 1 a, such as a PET film or an ON film, forming theoutermost layer of the battery case forming sheet 10 provides thebattery case forming sheet 10 with mechanical strength including tensilestrength, piercing strength and bending strength, and resistanceincluding abrasion resistance, water resistance, chemical resistance,heat resistance and low-temperature resistance. The metal foil layer,such as an aluminum foil layer, i.e., an intermediate layer, serves as abarrier layer impermeable to moisture and gases. The heat-adhesive resinlayer 3, i.e., the innermost layer, is a layer of an acid-denaturedpolyolefin resin having an acid content in the range of 0.01 to 10% byweight and provides the battery case forming sheet 10 with excellentheat-sealable property.

If the metal foil layer 2 is a 9 μm thick aluminum foil, the metal foillayer 2 has a water vapor permeability of 0.01 g/m²·24 hr or below at40° C. and 90% RH. The water vapor impermeability can easily beenhanced.

The following are representative examples of the foregoing laminatedsheet.

(1) PET (12 μm thick)/Aluminum foil (9 μm thick)/Acid-denaturedpolyolefin resin layer (15 μm thick)/PET (12 μm thick)/Acid-denaturedpolyolefin resin (30 μm thick)

(2) PET film (12 μm thick)/Aluminum foil (9 μm thick)/Acid-denaturedpolyolefin resin layer (15 μm thick)/ON (15 μm thick)/Acid-denaturedpolyolefin resin layer (30 μm thick)

(3) ON film (15 μm thick)/Aluminum foil (9 μm thick)/Acid-denaturedpolyolefin resin layer (15 μm thick)/PET (12 μm thick)/Acid-denaturedpolyolefin resin layer (30 μm thick)

(4) ON film (15 μm thick)/Aluminum foil (9 μm thick)/Acid-denaturedpolyolefin resin layer (15 μm thick)/ON (12 μm thick)/Acid-denaturedpolyolefin resin layer (30 μm thick)

The battery case forming sheet 10 is provided additionally with thethird base layer 1 c to improve various kinds of mechanical strength andresistance. Since the metal foil layer 2 is sandwiched between the firstbase layer 1 a and the third base layer 1 c, the metal foil layer 2 isprotected more securely from external and internal impacts, abrasion,physical and chemical actions, and provides more stable barrierproperty.

Referring to FIG. 35, a battery case forming sheet 10 is formed bysequentially laminating a first base layer 1 a, a metal foil layer 2, anadhesive resin layer 5, a third base layer 1 c, an adhesive resin layer4, an additional third base layer 1 d and a heat-adhesive resin layer 3.The first base film layer 1 a is the outermost layer.

The battery case forming sheet 10 is provided with the additional thirdbase layer id to improve the ability of the third base layer 1 c on theinner side of the intermediate metal foil layer 3, and the battery caseforming sheet 10 has an enhanced strength. Each of the first base layer1 a the third base layer 1 c and the additional third base layer id is aPET film or an ON film.

Although all the base layers may be the same types of films, it ispreferable to use different types of films, such as a PET film and an ONfilm as the first base layer 1 a, and the third base layer 1 c or theadditional third base layer 1 d, respectively, in view of complementingthe respective disadvantages and making the most of advantages of thefirst base layer 1 a, and the third base layer 1 c or the additionalthird base layer 1 d.

The battery case forming sheet 10 shown in FIG. 35 having the two baselayers on the inner side of the intermediate metal foil layer 2 issuperior in strength to the battery case forming sheet 10 shown in FIG.34. In those laminated sheets, whereas the adhesive layer 5 bondingtogether the first base layer 1 a and the metal foil layer 2 may beformed by either a dry lamination method or a sandwich laminationmethod, the layers of the laminated layer on the inner side of the metalfoil layer 2, i.e., the metal foil layer 2 and the third base layer 1 c,and the third base layer 1 c and the additional third base layer 1 d,are bonded together by a sandwich lamination method using the adhesiveresin layer 4, and the heat-adhesive resin layer 3 is formed by anextrusion coating method. The adhesive resin for use in the drylamination method and the resin for forming the heat-adhesive resinlayer are acid-denatured polyolefin resins.

The surface of the third base layer 1 c or the additional third baselayer 1 d may be finished by a well-known surface treatment, such ascorona treatment, flame treatment or plasma treatment, to improve theadhesion of the acid-denatured polyolefin resin to the surface. Thelaminated sheet may be compressed and heated (after heating) afterlaminating the component layers to enhance the adhesion between themetal foil layer or the base layer, and the heat-adhesive resin.

As shown in FIG. 35, the first base layer 1 a is formed on the outerside of the metal foil layer 2, and the adhesive resin layer 4, thethird base layer 1 c, the adhesive resin layer 4, the additional thirdbase layer 1 d and the heat-adhesive resin layer 3 are formed in thatorder on the inner side of the metal foil layer, The heat-adhesive resinlayer 3 is the innermost layer formed by an extrusion coating method.The metal foil layer 2 and the third base layer 1 c, the third baselayer 1 c and the additional third base layer 1 d are bonded together bya sandwich lamination method using an acid-denatured polyolefin resin.In this laminated sheet, it is desirable to use ON films for forming thethird base layer 1 c and the additional third base layer 1 d.

In this battery case forming sheet in accordance with the presentinvention, the base layers 1 a, 1 c and 1 d provides various kinds ofimproved mechanical strength and resistance, the metal foil layer 2 issandwiched between the first base layer 1 a and the third base layer 1c, and the additional third base layer 1 d is laminated to the thirdbase layer 1 c to provide the battery case forming sheet with animproved barrier property by protecting the metal foil layer 2 from apiercing action from inside.

When printing a picture of letters and patterns on the surface of eachof the battery case forming sheets 10 shown in FIGS. 34 and 35, thepicture is printed on the inner surface of the first base layer 1 a tobe bonded to the surface of the adjacent layer for second-surfacedecoration, and then the first base film layer is laminated to theadjacent layer. The thus printed picture will not be damaged even if thesurface of the sheet 10 is abraded.

As is apparent form the foregoing description, the present inventionprovides lightweight, thin, flexible, battery case forming sheetsexcellent in various kinds of mechanical strength, heat-resistance,impermeability to moisture and gases, heat-sealability andprocessability, and capable of being efficiently produced.

Since the inner laminated layer on the inner side of the metal foillayer is formed without using adhesive layers of a solvent-dissolvableadhesive, the inner laminated layer will not be caused to delaminate bythe electrolyte of a battery.

Since the adhesive resin layer and the heat-adhesive resin layer areformed of acid-denatured polyolefin resins having a meting point of 100°C., there is no possibility that the sealed parts of the battery caseare unsealed and the electrolyte leaks when the battery packet isexposed to high temperatures.

Tenth Embodiment

Battery packets in a tenth embodiment according to the present inventionwill be described with reference to FIGS. 37 to 44. A battery packet inthe tenth embodiment using a battery case is featured by terminalscovered with an insulating sheet provided with at least one opening foreach terminal in a part thereof extending outside the battery case. Theouter surface of the insulating sheet is bonded by heat-sealing to theinner surface of the battery case, the insulating sheet has at least onesurface provided with a layer capable of being bonded to the terminals,the insulating sheet has a base layer of a polyethylene terephthalateresin, a polyamide resin, a polyimide resin or a polycarbonate resin,and the battery case and/or the insulating sheet is printed with apicture. The tenth embodiment is substantially the same in otherrespects as the first embodiment.

The battery packet in accordance with the present invention is a thinbattery packet formed by sealing a battery in a battery case, flat tabsare extended from the battery, the tabs are covered with an insulatingfilm, and openings are formed in predetermined parts of the insulatingfilm to connect the battery to a device to be powered by the battery.

FIG. 37(a) is a perspective view of a battery packet, FIG. 37(b) is aperspective view of a battery provided with terminals covered with aprotective film, and FIG. 37(c) is a sectional view taken on line X₁—X₁(X₂—X₂) in FIG. 37(a).

FIGS. 38(a) and 38(b) are perspective views of assistance in explaininga method of covering electrodes with an insulating film, showing a statebefore covering and a state after covering, respectively. FIG. 39(a) isa perspective view of a battery case in a preferred embodiment accordingto the present invention in a state before sealing a battery therein andFIG. 39(b) is a sectional view taken on line X₂—X₂ in FIG. 39(a). FIG.40 is a top view of a battery packet having electrodes of a constructionsimilar to that of the battery case in the foregoing embodiment. FIG.41(a) is a sectional view taken on line X₃—X₃ (X₄—X₄) in FIG. 40, FIG.41(b) is an enlarged view of a part W in FIG. 41(a), FIG. 42(a) is asectional view taken on line Y₁—Y₁ in FIG. 40, FIG. 42(b) is a sectionalview taken on line Y₂—Y₂ in FIG. 42(a), FIGS. 43(a), 43(b) and 43(c) aretypical sectional views of assistance in explaining the constitution ofan electrode protecting film in accordance with the present invention,FIG. 44(a) is a typical sectional view of a prior art battery case, FIG.44(b) is a prior art battery packet, and FIG. 44(c) is an enlarged viewtaken along the direction of the arrow Z.

Referring to FIGS. 44(a) and 44(c), when a flexible packaging sheet 10forming a battery case 51 is provided with a conductive layer 2, such asa metal foil, the conductive layer 2 of the packaging sheet 10 isexposed in an end surface 10 a of the battery case 51, and it ispossible that accidental contact between tabs 59 and 60, and the edge ofthe conductive layer 2 exposed in the end surface 10 a occurs if thetabs 59 and 60 are flexible sheets, such as metal foils. The sheet 10 isformed by laminating a first base film layer 1 a, a metal foil layer 2,a third base film layer 1 c, a heat-adhesive resin layer 3 by usingadhesive layers 5 a and 5 b.

If such accidental contact occurs, the electromotive force of thebattery decreases or decreases to zero due to discharge. If suchaccidental contact occurs in a device loaded with the battery, thedevice may possibly malfunction or break.

The inventors of the present invention made earnest studies to solvesuch a problem and solved the problem by forming the electrodes in thefollowing construction.

As shown in FIG. 37, exposed parts of strip-shaped tabs 59 and 60projecting outward from an end of a battery case 51 are covered with aninsulating electrode protecting film 61 to prevent accidental contact.

There is not any particular restrictions on the method of covering thetabs 59 and 60 with the electrode protecting film 61, except that thetabs 59 and 60 should not entirely be covered and at least contact partsof the tabs 59 and 60 to be brought into contact with the inputterminals of a device to be powered by the battery packet (hereinafterreferred to as “contact parts”) must be exposed.

More specifically, openings 62 are formed in the electrode protectingfilm 61, and the electrode protecting film 61 is put on the tabs 59 and60 so as to cover both the surfaces of the tabs 59 and 60. In thisstate, contact parts of the tabs 59 and 60 corresponding to the openings62 are exposed for connection to the input terminals of the device.

The electrode protecting film 61 must be attached to the tabs 59 and 60carefully with an adhesive so as not to cover the contact parts with aninsulating film of the adhesive.

Although it is desirable to use a heat-sealing method for forming thebattery case 51 of the present invention, a method using an adhesive maybe used instead of the heat-sealing method, provided that the batterycase 51 and the electrode structure meeting the present invention can beformed.

Materials for forming the battery case 51 must be capable of forming asealed structure and of maintaining a satisfactory barrier property notto permit moisture and corrosive gases to pass through into the batterycase 51 for a very long period, and have heat resistance andlow-temperature resistance as basic thermal conditions. Materialsforming the outermost and the innermost layer of the battery case mustbe electrically nonconductive.

A battery case forming sheet 10 having such required physical propertiescan be formed by various kinds of materials. Desirably, the battery caseforming sheet is a laminated sheet formed by laminating flexible filmsand a metal foil. Such a laminated sheet is able to make the most ofexcellent physical properties of the films and the metal foil, and tomake the films and the metal foil complement each other.

The case 51 may be formed by any one of suitable methods including amethod using an adhesive, a method using ultrasonic waves, a methodusing high-frequency waves and a heat-sealing method using heat andpressure.

According to the present invention, it is desirable that the inner layerof the laminated sheet for forming the case 51 is formed of aheat-adhesive material, and the case is formed by heat-sealing necessaryparts of the laminated sheet.

The battery case forming laminated sheet 10 of the present inventionwill be concretely be described.

FIG. 37(d) shows an example of the laminated sheet. The construction ofthe laminated sheet is:

Outermost layer 1 a/Barrier layer 2/Reinforcing layer 1 c/Sealant layer3 (innermost layer)

Those layers are laminated by dry lamination or sandwich lamination.

Preferably, the thickness of the laminated sheet is in the range of 50to 200 μm. A laminated sheet of a thickness below 50 μm is inferior inimpermeability to moisture and may possibly permit moisture to passthrough into the electrolyte. A laminated sheet of a thickness exceeding200 μm does not conform to a basic idea of providing a polymer batterypacket of the least possible weight and thickness, and the effect of alaminated sheet of such a great thickness in not permitting moisture andgases to pass through cannot be expected to be as great as itsthickness.

Materials of the layers of the laminated sheet are selectivelydetermined according to desired physical properties of the laminatedsheet.

Concrete construction of the laminated sheet may be:

PET (outermost layer)/AL/PET (or Ny)/Sealant (innermost layer)

PET: polyethylene terephthalate, AL: aluminum (foil), Ny: nylon

The outermost layer (first base film layer) 1 a is the outer surfacelayer of a battery case. Therefore, the outermost layer 1 a must beelectrically nonconductive, must have a smooth surface, must besufficiently resistant to chemicals and abrasion, must have sufficientlyhigh tensile and piercing strength, and must be capable of protecting abattery from external, detrimental, destructive, physical and chemicalactions. Biaxially oriented films of resins, particularly, biaxiallyoriented films of PET resins are preferable materials for forming theoutermost layer 1 a.

A desirable thickness of the outermost layer 1 a is in the range of 5 to30 μm. If the thickness of the outermost layer 1 a is below 5 μm, thepiercing strength of the outermost layer 1 a is insufficient and it ishighly possible that pinholes are formed in the outermost layer 1 a. Ifthe thickness of the outermost layer 1 a is above 30 μm, the outermostlayer 1 a will adversely affect the heat-sealability of the laminatedsheet.

It is preferable to form the barrier layer (metal foil layer) 2contiguously with the outermost layer 1 a. The barrier layer 2 hasbarrier property to prevent moisture and gases from permeating thebattery case. Suitable materials for forming the barrier layer 2 arefilms of ethylene-vinyl alcohol copolymers and the like, coated filmsproduced by coating polyethylene terephthalate films and the like withmetals, silicon dioxide and inorganic oxides by evaporation, and coatedfilms produced by coating films with barrier coating agents includingpolyvinylidene chloride resins. It is more preferable to use a metalfoil, such as an aluminum foil, as the barrier layer 2. Desirably, analuminum foil for forming the barrier layer 2 has a thickness in therange of 5 to 30 μm. Aluminum foils of a thickness below 5 μm has manypinholes and are inferior in barrier property. Aluminum foils of athickness above 30 μm affect adversely to the heat-sealability of thelaminated sheet when forming a case.

It is preferable to form the reinforcing layer (third base film layer) 1c on the inner surface of the barrier layer 2 to reinforce the strengthof a battery case formed by processing the laminated sheet. It isparticularly desirable to reinforce a battery case against thescratching and piecing actions of sharp projections. The reinforcinglayer 1 c may be a biaxially oriented resin film, preferably, abiaxially oriented PET or Ny film. Desirably, the reinforcing layer 1 chas a thickness in the range of 5 to 30 μm. The reinforcing layer 1 c isinferior in resistance to the piercing action of a battery contained inthe case, pinholes are liable to be formed in the reinforcing layer 1 c,and it is possible that the electrolyte leaks and the laminated sheetdelaminates if its thickness is below 5 μm. The reinforcing layer 1 cwill adversely affect the sealability of the laminated sheet if itsthickness is above 30 μm.

Necessary parts of the sealant layer (heat-adhesive resin layer 3) ofthe laminated sheet are bonded together by heat-sealing when forming thebattery case 21. As mentioned above, it is desirable, in view offacility in operation and sealing capability, to form the battery caseby processing the laminated sheet by a heat-sealing method. Whennecessary parts of the sealant layer of the laminated sheet arebonded.together by a heat-sealing method, the sealant layer is formed ofa heat-adhesive material. The heat-adhesive material must beheat-adhesive to the tabs 59 and 60, or the electrode protecting film61.

The sealant layer 3 is formed of a material heat-adhesive to itself andto metal foils forming the terminals, or the electrode protecting film.Materials suitable for forming the sealant layer 3 are, for example,ethylene-acrylic acid resins (EAA), ethylene-methacrylic acid resins(EMAA), ethylene-ethylacrylate resins (EEA) and ionomers.

The sealant layer 3 may be formed either by laminating a film of one ofthe foregoing resins to the reinforcing layer 1 c or by melting andextruding one of the foregoing resins over the surface of thereinforcing layer 1 c by an extruder.

Desirably, the thickness of the sealant layer 3 is in the range of 10 to100 μm. If the thickness of the sealant layer 3 is below 10 μm, thepiercing strength of the sealant layer 3 is insufficient and it ishighly possible that pinholes are formed in the sealant layer 3 and itis possible that the electrolyte leaks and the laminated sheetdelaminates. If the thickness of the sealant layer is greater than 100μm, the amount of moisture absorbed by the sealant layer 3 is large andit is possible that moisture permeates the sealant layer 3.

As mentioned above, the outermost layer 1 a, the barrier layer 2, thereinforcing layer 1 c and the sealant layer 3 may be laminated by drylamination using a polyurethane adhesive or by sandwich lamination whichextrudes an adhesive resin between the adjacent layers.

Terminals relating with the present invention will be described below.The tabs 59 and 60 are flat terminals of a metal foil or the like. Asmentioned above, exposed parts of the tabs 59 and 60 excluding thecontact parts to be brought into contact with the input terminals of adevice to be powered by the battery packet are covered with theinsulating electrode protecting film 61. Particularly, the parts of thetabs 59 and 60 corresponding to the end edge 10 a of the battery case 51are securely covered to prevent troubles due to the accidental contactbetween the tabs 59 and 60, and the conductive layer 2 exposed in theend edge 10 a of the battery case 51.

Referring to FIG. 38(a), openings 62 are formed in predetermined partsof the electrode protecting film 61 and the electrode protecting film 61is folded in two leaves. The openings 62 are formed so as to correspondto the contact parts of the tabs 59 and 60 when the electrode protectingfilm 61 is folded in two leaves. The tabs 59 and 60 are disposed betweenthe halves of the folded electrode protecting film 61, the halves of theelectrode protecting film 61 are bonded together by heat-sealing or thelike so as to sandwich the tabs 59 and 60 therebetween.

The tabs 59 and 60 may be covered with the electrode protecting film 61by spreading an adhesive over the inner surface of the electrodeprotecting film 61, folding the electrode protecting film 61 in twoleaves so as to sandwich the tabs 59 and 60, and compressing the foldedelectrode protecting film 61 and the tabs 59 and 60 for a predeterminedtime.

Although the tabs 59 and 60 may have uncovered parts 67 near the battery50 a in the battery case 51.

The electrode protecting film 61 covering the tabs 59 and 60 will bedescribed below. The electrode protecting film 61 may be of any type,provided that the same is electrically nonconductive and capable ofbeing bonded by heat-sealing to the tabs 59 and 60. The electrodeprotecting film 61 may be a film (adhesive layer 71) as shown in FIG.43(a), a two-layer film consisting of a support layer 72 and an adhesivelayer 71 as shown in FIG. 43(b) or a three-layer film consisting of anadhesive layer 71, an outer layer 73, and a support layer 72 sandwichedbetween the adhesive layer 71 and the outer layer 73 as shown in FIG.43(c).

As mentioned above, it is preferable to cover the terminals with theelectrode protecting film by a heat-sealing method similarly to formingthe battery case by a heat-sealing method.

The adhesive layer 71 and the outer layer 73 of the electrode protectingfilm 61 are formed of materials heat-adhesive to the metal foils formingthe terminals, such as ethylene-acrylic acid resins (EAA),ethylene-methacrylic acid resins (EMAA), ethylene-ethylacrylate resins(EEA) and ionomers.

The support layer 72 is formed of a film dimensionally stable whenheated and having a high tensile strength. Preferable materials forforming the support layer 72 are biaxially oriented films ofpolyethylene terephthalate resins, polyamide resins, polyimide resins,polycarbonate resins.

The electrodes are flat strips of a conductive material. Suitablematerials for forming the electrodes are foils of metals includingaluminum, copper and tin, and alloys of some of those metals.

The electrode protecting film 61 employed in the present invention willbe described. The exposed parts of the tabs 59 and 60 excluding thecontact parts to be brought into contact with the input terminals of adevice to be powered by the battery packet are covered with theinsulating electrode protecting film 61. Although other parts of thetabs 59 and 60 may be either covered or not covered, it is desirable tocover the largest possible parts of the tabs 59 and 60 excluding thecontact parts with the electrode protecting film 61 because theelectrodes projecting from the battery case are flexible and it ispossible that the tabs 59 and 60 are deformed before or during the useof the battery packet and the battery cannot properly be connected to adevice.

As shown in FIG. 38, the openings 62 are formed in predetermined partsof the electrode protecting film 61 and the electrode protecting film 61is folded in two leaves. The openings 62 are formed so as to correspondto the contact parts of the tabs 59 and 60 when the electrode protectingfilm 61 is folded in two leaves and put on the tabs 59 and 60. Thefolded electrode protecting film 61 is put on the tabs 59 and 60 so asto cover both the surfaces of the tabs 59 and 60 and to extend beyondthe outer sides of the tabs 59 and 60.

Thus the contact parts of the tabs 59 and 60 are exposed in the openings62 to serve as the terminals of the battery 50. The openings may beformed in the electrode protecting film 61 either only on one side ofthe tabs 59 and 60 or on both sides of the same. It is also possible toform the openings so that the end edge parts of the tabs 59 and 60 orthe respective outer side edge parts of the tabs 59 and 60 are exposedwhen the tabs 59 and 60 are covered with the electrode protecting film61.

The tabs 59 and 60 must be covered with the electrode protecting film 61so that the surfaces of the contact parts are exposed. At least thelayer to be bonded to the tabs 59 and 60 of the electrode protectingfilm 61 is formed of a material heat-adhesive to the tabs 59 and 60. Theopenings 62 are formed in the electrode protecting film 61, and then theelectrode protecting film 61 is bonded by heat-sealing to the tabs 59and 60. When an adhesive is spread over the surface of the electrodeprotective film 61 to bond the electrode protective film 61 to the tabs59 and 60, the openings 62 are formed first in the electrode protectivefilm 61, and then the surface of the electrode protective film 61excluding regions corresponding to the openings 62 is coated with theadhesive. Then, the electrode protective film 61 is bonded to the tabs59 and 60.

Most preferably, the electrode protective film 61 has at least oneheat-adhesive layer of a material heat-adhesive to the tabs 59 and 60 onone side thereof, is provided with the openings 62, the electrodeprotective film 61 is folded in two laves to sandwich the tabs 59 and 60between the two parts of the heat-adhesive layer, and the combination ofthe electrode protective film 61 and the tabs 59 and 60 is heated andcompressed to cover the tabs 59 and 60 with the electrode protectivefilm 61.

Since the electrodes projecting outside from the battery case are thuscovered, troubles due to the accidental contact between the tabs 59 and60, and the conductive layer 2 exposed in the end edge 10 a of thebattery case 51 can be prevented and the parts of the tabs 59 and 60extending outside the battery case 51 are reinforced.

The battery case 51 in accordance with the present invention is formedby processing the laminated sheet. The outermost layer 1 a may be atransparent film and trade name, and directions for use or precautionarystatement may be printed oh the transparent film. When necessary,information can be printed on the electrode protecting film 61. Wheninformation needs to be printed on the electrode protecting film 61, alaminated film formed by laminating the support layer 72 printed on itsinner surface with information, the adhesive layer 71 and/or the outerlayer 72 is used as the electrode protecting film 61. Since a printedlayer thus formed can be formed by backing printing between otherlayers, the printed layer will not be abraded and may be formed byprinting an ordinary printing ink which is not particularlyabrasion-resistant.

EXAMPLES

A sheet 10 for forming the battery case 51 was formed by the followingprocedure. A 15 μm thick aluminum foil (commercially available fromMitsubishi Aluminum Co.) as the barrier layer 2, i.e., an intermediatelayer, was laminated to a 12 μm thick polyethylene terephthalate film(“RUMIRA” commercially available from Toray Industries, Inc.) as theoutermost layer 1 a with a two-component polyurethane adhesive.

The polyurethane adhesive has isocyanate (“TAKERAKKU A511” commerciallyavailable from Takeda Chemical Industries, Ltd.) as a main component,and a polyol (“POLYOL A50” commercially available from Takeda chemicalIndustries, Ltd.). The coating weight per unit area of the two-componentpolyurethane adhesive was in the range of 3 to 5 g/m².

A 12 μm thick biaxially oriented nylon film (“ENBUREMU” commerciallyavailable from Yunichika K.K.) as the reinforcing layer 1 c waslaminated to the surface of the aluminum foil by a dry lamination usingthe same polyurethane adhesive, and then a 50 μm thick layer of anethylene-methacrylic acid resin (EMAA) (“NYUKURERU” commerciallyavailable from Mitsui Porikemikaru K.K.) was formed as the sealant layer3 over the surface of the nylon film by an extrusion method.

A film to be used as the electrode protecting film 61 was formed by thefollowing procedure. Two 20 μm thick layers of an ethylene-methacrylicacid resin (EMAA) (“NYUKURERU” commercially available from MitsuiPorikemikaru K.K.) were formed on both the surfaces of a 12 μm thickpolyethylene terephthalate film (“RUMIRA” commercially available fromToray Industries, Inc.) by an extrusion method.

Then, the battery case 51 having a sealed part 65 and an open end 66 asshown in FIG. 39(a) was fabricated by processing the sheet 10. The tabs59 and 60 extending from the battery 50 a were copper foil strips of 40μm in thickness, 15 mm in width and 30 mm in length openings 62 wereformed in the electrode protecting film and the tabs 59 and 60 werecovered with the electrode protecting film by the method previouslydescribed with reference to FIG. 38.

The battery 50 a provided with the tabs 59 and 60 extending therefromand covered with the electrode protecting film 61 was inserted throughthe open end 66 into the battery case 51, and the open end 66 washeat-sealed to sandwich the tabs 59 and 60 covered with the electrodeprotecting film 61 between the edge parts of the open end 66 of thebattery case 51 to complete a polymer battery packet 50 as shown in FIG.40.

In this example, the opening 62 (and the contact parts 10 of the tabs 59and 60) are elliptic, and both the surfaces of the contact parts of thetabs 59 and 60 were exposed.

As shown in FIGS. 41 and 42, in the electrode structure of the batterycase 51 of the polymer battery packet 50, the openings 62 of theelectrode protecting film 61 (the contact parts of the tabs 59 and 60)are formed at positions near the extremities of the tabs 59 and 60, andparts of the tabs 59 and 60 near the end edge 10 a of the battery case51 are covered with the insulating electrode protecting film 61.Therefore, there is no possibility of troubles due to short-circuitingat all.

In the electrode structure of the battery case 51 covered with theelectrode protecting film 61, the tabs 59 and 60 are not short-circuitedeven if the tabs 59 and 60 are bent, the electrodes are difficult tobend, and the tabs 59 and 60 are reinforced.

The electrodes are never short-circuited by the metal foil of thelaminated sheet forming the battery case, and the stable functioning ofthe case and the electrodes can be ensured.

Since the electrodes are covered with the insulating sheet, the rigidityof the terminal part extending from the end edge of the battery case isenhanced, the terminals are never bent while the battery is used, andthe stability of the terminals are improved.

Eleventh Embodiment

An eleventh embodiment according to the present invention will bedescribed with reference to FIGS. 45 to 48, in which parts like orcorresponding to those of the first embodiment are designated by thesame reference characters and the description thereof will be omitted.

The construction and functions when a gas is produced of a battery inaccordance with the present invention will be described with referenceto the accompanying drawings.

FIG. 45(a) is a top view of a polymer battery packet in the eleventhembodiment, FIG. 45(b) is a sectional view taken on line X₁—X₁ in FIG.45(a) in a state where the polymer battery packet is tuned on, FIG.45(c) is a sectional view taken on line X₁—X₁ in FIG. 45(a) in a statewhere the polymer battery packet is tuned off, FIG. 45(d) is an enlargedview of a part Y₁ in FIG. 45(b), and FIG. 45(e) is an enlarge view of apart Y₂ in FIG. 45(c). FIG. 46(a) is a perspective view of a pressingdevice in accordance with the present invention employing a platespring, FIG. 46(b) is a perspective view of a pressing device inaccordance with the present invention employing a coil spring, FIG.46(c) is a sectional view taken on line X₂—X₂ in FIG. 46(a), and FIG.46(d) is a sectional view taken on line X₃—X₃ in FIG. 46(b). FIG. 47 isa schematic sectional view of a pressing device in accordance with thepresent invention mounted on a device to be powered by a polymer batterypacket, and FIG. 48 is a typical sectional view of a laminated sheet forforming a battery case for a polymer battery packet in accordance withthe present invention.

The present invention incorporates a mechanism for turning off thebattery of the polymer battery packet when a gas is produced in thebattery case of the polymer battery packet without changing the basicconstruction of the polymer battery packet.

A laminated film for forming the battery case of the polymer batterypacket has various kinds of strength and resistance, barrier propertynot permitting moisture and gases to pass through and heat-sealability.One or each of both of tabs has a first part extending from the batteryto a middle position between the battery and the sealed end of thebattery case, and a second part extending from the middle positionthrough the sealed end of the battery case outside the battery case, andthe corresponding end parts of the first and the second part of the taboverlap each other so as to be electrically connected to form an overlapcontact part.

Referring to FIGS. 45(a) and 45(b) showing the polymer battery packet inthe eleventh embodiment according to the present invention, a batterycase 51 has the shape of a pouch having four sealed side parts, and abattery 50 a is sealed in the battery case 51. Tabs 59 and 60 extendfrom the battery 50 a through a sealed end 78 of the battery case 51.The tab 59 has a first part 59a extending between the battery 50 a and aposition slightly beyond a middle position between the battery 50 a andthe sealed part 78, and a second part 59 b extending from a positionslightly behind the middle position through the sealed part 78 outsidethe battery case 51 so that corresponding end parts of the first part 59a and the second part 59 b overlap each other to form an overlap contactpart 77. The tab 60 has a first part 60 a extending between the battery50 a and a position slightly beyond a middle position between thebattery 50 a and the sealed part 78, and a second part 60 b extendingfrom a position slightly behind the middle position through the sealedpart 78 outside the battery case 51 so that corresponding end parts ofthe first part 60 a and the second part 60 b overlap each other to forman overlap contact part 77.

The battery 50 a is able to supply power when the tabs 59 and 60 are ina state shown in FIG. 45(b).

The polymer battery packet 50 is fabricated by assembling the componentmaterials of the battery including an electrolyte, an electrolytesupport impregnated with the electrolyte, a positive electrode, anegative electrode and tabs in the battery case 51, evacuating thebattery case 51, and hermetically sealing the battery case 51. In thenormal state, the overlap contact part 77 remains connected because thebattery case 51 is compressed by the atmospheric pressure as shown inFIG. 45(b) or 45(d), and the first part 59 a (60 a) of the tab 59 (60)and the second part 59 b (60 b) of the same are kept in contact witheach other.

If a gas is produced in the battery case 51 of the polymer batterypacket 50, the pressure in the battery case 51 increases and a part ofthe battery case 51 around the overlap contact part 77 is expanded asindicated by the arrows in FIG. 45(d), and the same part of the batterycase 51 is expanded further to a state shown in FIG. 45(e) as thepressure in the battery case 51 further increases. Consequently, thefirst part 59 a (60 a) and the second part 59 b (60 b) of the tab 59(60) are disconnected from each other, the overlap contact part 77becomes disconnected and, consequently, the polymer battery packet 50 isturned off. As is obvious from FIG. 45(e), the overlap contact part 77can more surely be disconnected if the tabs 59 (60) is attachedadhesively to the inner surfaces of the battery case 51.

If the first part 59 a (60 a) is attached to the lower wall of thebattery case 51 and the second part 59 b (60 b) is attached to the upperwall of the battery case 51, the overlap contact part 77 can more surelybe disconnected when a gas is produced in the battery case 51.

The polymer battery packet 50 in accordance with the present inventionmay be contained in an outer battery case 51 a of a hard material inview of facility in handling and protection from external pressure. Whenthe polymer battery packet 50 is contained in such an outer battery case51 a of a hard material, a pressing device may be disposed in the outerbattery case 51 a to press the overlap contact part with reliability.

The pressing device may press the overlap contact part 77 by anysuitable method, provided that the pressing device allows the overlapcontact part 77 to become disconnected to interrupt a current when a gasis produced in the polymer battery packet 50 and the pressure in thebattery case of the polymer battery packet 50 increases.

For example, the pressing device may be provided with a plate spring 76Pdisposed inside the outer battery case 51 a as shown in FIG. 46(a) ormay be provided with a coil spring 76S disposed inside the outer batterycase 51 a as shown in FIG. 46(b).

Although the pressing devices shown in FIG. 46 are typical onesemploying a spring, there is not any restrictions on materials andconstruction of the pressing devices, provided that the pressing devicescan be caused to release pressure from the overlap contact part by thepressure of the gas.

For example, the overlap contact part 77 may be pressed by an elasticmember, not shown, set in a height so as to exert a compressive force onthe lid of the outer battery case 51 a at a position for depressing theoverlap contact part 77.

Although the pressing device is attached to the inner surface of theouter battery case 51 a in the polymer battery packet 50 in accordancewith the present invention, the pressing device may be disposed in thebattery chamber of a device 79 to be powered by the polymer batterypacket 50.

As mentioned above, the battery case 51 in accordance with the presentinvention is formed of a flexible laminated sheet formed by laminatingmaterials having properties capable of providing the battery case 51with required functions. The laminated sheet is shaped in a pouch, thebattery is placed in the pouch and the pouch is sealed to complete thepolymer battery packet 50.

Basically, the laminated sheet comprises a first base film layer 1 a, ametal foil layer 2, a third base film layer 1 c and the heat-adhesiveresin layer 3 as shown in FIG. 48.

Materials for forming the polymer battery packet 50 in accordance withthe present invention and the construction of the laminated sheetforming the battery case 51 will be described hereinafter. In most casesthe tabs 59 and 60 of the electrode structure in accordance with thepresent invention are metal foils, such as aluminum foils or copperfoils, and the battery case 51 is formed of a flexible laminated sheet.

The battery case 51 containing the polymer battery 50 a is formed of alaminated sheet impermeable to moisture and corrosive gases and capableof protecting the polymer battery 50 a from damage that may be caused bypiecing and abrasion and the like during transportation and use.

A laminated sheet 10 formed in the construction as shown in FIG. 48 maybe used.

(Outer side) Outermost layer/Barrier layer/Reinforcing layer/Sealantlayer (Inner side)

These layers can be laminated by dry lamination or sandwich lamination.

Preferably, the thickness of the laminated sheet 10 is in the range of50 to 400 μm. A laminated sheet of a thickness below 50 μm is inferiorin impermeability to moisture and strength, and may possibly permitmoisture to pass through into the electrolyte. A laminated sheet of athickness exceeding 400 μm has inferior heat-sealability, increases theweight of the battery and case does not conform to a basic idea ofproviding a polymer battery packet of the least possible weight. Theeffect of a laminated sheet of a thickness exceeding 400 μm in notpermitting moisture and gases to pass through cannot be expected to beas great as its thickness. Materials of the layers of the laminatedsheet are selectively determined according to desired physicalproperties of the laminated sheet. The following is an example of thematerials and the construction of the laminated sheet.

(Outer side) PET/AL/PET (or Ny)/EMAA (Inner side) where PET is apolyethylene terephthalate resin, AL is aluminum (foil), Ny is a nylonresin, and EMAA is an ethylene-methacrylic acid copolymer.

The outermost layer (first base film layer) 1 a is the outer surfacelayer of a battery case. Therefore, the outermost layer 1 a must beelectrically nonconductive, must have a smooth surface, must besufficiently resistant to chemicals and abrasion, must have sufficientlyhigh tensile and piercing strength, and must be capable of protecting adevice from external, detrimental, destructive, physical and chemicalactions. Biaxially oriented films of resins, particularly, biaxiallyoriented films of PET resins are preferable materials for forming theoutermost layer 1 a. A desirable thickness of the outermost layer 1 a isin the range of 5 to 30 μm. If the thickness of the outermost layer 1 ais below 5 μm the piercing strength of the outermost layer 1 a isinsufficient and it is highly possible that pinholes are formed in theoutermost layer 1 a. If the thickness of the outermost layer 1 a isabove 30 μm, the outermost layer 1 a will adversely affect theheat-sealability of the laminated sheet and will reduce productionefficiency.

It is preferable to form the barrier layer (metal foil layer) 2contiguously with the outermost layer 1 a. The barrier layer 2 hasbarrier property to prevent moisture and gases from permeating thebattery case. It is desirable to use a metal foil, such as an aluminumfoil, as the barrier layer 2. Desirably, an aluminum foil for formingthe barrier layer 2 has a thickness in the range of 5 to 30 μm. Aluminumfoils of a thickness below 5 μm has many pinholes and are inferior inbarrier property. Aluminum foils of a thickness above 30 μm affectadversely to the production of the battery case. When a battery case isformed of a laminated sheet provided with a metal foil, such as analuminum foil, it is possible that tabs T are short-circuited by anexposed edge of the conductive metal foil. Although troubles includingshort circuit can be avoided if the barrier layer 2 is formed of anonconductive material, the use of such a material inevitably entailsreduction in the barrier property of the laminated sheet.

It is preferable to form the reinforcing layer (third base film layer) 1c on the inner surface of the barrier layer 2 to reinforce the strengthof a battery case 51 formed by processing the laminated sheet. It isparticularly desirable to reinforce a battery case against the damagingactions of sharp projections. The reinforcing layer 1 c may be abiaxially oriented resin film, preferably, a biaxially orientedpolyethylene terephthalate or nylon film. Desirably, the reinforcinglayer 1 c has a thickness in the range of 5 to 30 μm. The reinforcinglayer 1 c is inferior in resistance to the piercing action of a battery50 a contained in the battery case, pinholes are liable to be formed inthe reinforcing layer 1 c if its thickness is below 5 μm. Thereinforcing layer 1 c will adversely affect the sealability of thelaminated sheet if its thickness is above 30 μm.

The innermost layer of the laminated sheet 10 forming the battery case51 is a heat-adhesive resin layer 3. Necessary parts of theheat-adhesive resin layer 3 are bonded together by heat-sealing whenforming the battery case 51. As mentioned above, it is desirable, inview of facility in operation and sealing capability, to form thebattery case by processing the laminated sheet by a heat-sealing method.When the battery case 51 is formed by a heat-sealing method, theheat-adhesive resin layer 3 is formed of a heat-adhesive material. Theheat-adhesive material must be heat-adhesive to itself and to the metalfoils forming the tabs T. Desirable materials for forming theheat-adhesive layer 3 are polyolefin copolymers includingethylene-acrylic acid resins (EAA), ethylene-methacrylic acid resins(EMAA), ethylene-ethylacrylate resins (EEA) and ionomers.

The heat-adhesive resin layer 3 may be formed either by laminating afilm of one of the foregoing resins to the reinforcing layer 1 c or bymelting and extruding one of the foregoing resins over the surface ofthe reinforcing layer 1 c by an extruder. Desirably, the thickness ofthe heat-adhesive resin layer 3 is in the range of 10 to 100 μm. If thethickness of the heat-adhesive resin layer 3 is below 10 μm, thepiercing strength of the heat-adhesive resin layer 3 is insufficient andit is highly possible that pinholes are formed in the heat-adhesiveresin layer 3. If the thickness of the heat-adhesive resin layer 3 isgreater than 100 μm, a heat-sealing operation for forming the batterycase 51 takes much time and reduces production efficiency.

As mentioned above, the outermost layer 1 a, the barrier layer 2, thereinforcing layer 1 c and the heat-adhesive resin layer 3 may belaminated by dry lamination using a polyurethane adhesive or by sandwichlamination in which adhesive resin are extruded between the adjacentlayers.

The hard outer battery case 51 a containing the polymer battery packet50 in accordance with the present invention is made of a hard material,usually, a hard plastic material, in a flat shape by an injectionmolding method. Suitable plastic materials for forming the hard outerbattery case 51 a are polyethylene resins, polypropylene resins,polyester resins, polyamide resins, polycarbonate resins, polystyreneresins, acrylonitrile butadiene styrene resins and polyurethane resins.

As is apparent from the foregoing description, according to the presentinvention, the polymer battery packet can be turned off without breakingthe battery case 51 and hence the contents will not be scattered.

The operating pressure of the pressing device can optionally bedetermined by using the spring capable of being moved so as to removepressure from the overlap contact part when the pressure in the batterycase rises, the polymer battery packet has a simple construction and canefficiently be produced.

Whereas the principal object of a conventional safety means for apolymer battery packet is gas purging, the battery case of the polymerbattery packet in accordance with the present invention does not permita gas produced therein to leak.

EXAMPLES

A trial thin polymer battery packet having the following battery caseand tab structure was fabricated and the performance of the same wasevaluated.

Polymer battery packet

Battery case: A pouch of 60 mm×95 mm in external size with three sealedsides

Overlap contact part: Positive tab of 5 mm in width with an overlapcontact part of 5 mm in length

Laminated sheet forming the battery case:

PET (12 μm thick)/AL (15 μm thick)/DL/ON (15 μm thick)/Acid-denaturedpolyolefin^(*1) (40 μm thick)

Note: ON: Biaxially oriented nylon film

*1: ADOMA NF0060 commercially available from Mitsui Sekiyu Kagaku KogyoK.K.)

The tabs were attached by point heat-sealing similar to spot welding tothe inner surface of the battery case.

The battery case was sealed by a vacuum packaging machine. A rubbervalve to blow air into the battery case of the polymer battery packetwas attached to the battery case. The polymer battery packet was loadedinto a device. The supply of power was interrupted when air was blownthrough the rubber valve into the battery case while power was beingsupplied from the polymer battery packet.

The polymer battery packet was contained in an outer case made of an ABSresin, and the overlap contact part was pressed by a disk of 3 mm² inarea.

The polymer battery packet contained in the outer case was loaded intothe device. The supply of power was interrupted when air was blown intothe battery case while power was being supplied from the polymer batterypacket.

The polymer battery packet in accordance with the present invention canbe tuned off without breaking the battery case when a gas is produced inthe battery case. Therefore, the contents of the battery case will notbe scattered.

Since the supply of power is interrupted by the action of the springcapable of being moved by the pressure in the battery case, theoperating pressure of the pressing device can optionally be determinedwithout taking into consideration temperature and contents.

The strength of the pouch need not be reduced and the pressing device isable to operate stably at a very low pressure.

Twelfth Embodiment

A twelfth embodiment according to the present invention will bedescribed with reference to FIGS. 49 to 54, in which parts like orcorresponding to those of the first embodiment are designated by thesame reference characters and the description thereof:will be omitted.

FIG. 49(a) is a perspective view of a battery packet in accordance withthe present invention provided with tabs, FIG. 49(b) is an enlarged viewof a part G₁ in FIG. 49(a), FIG. 49(c) is an enlarged sectional viewtaken on line X₁—X₁ in FIG. 49(b) and FIG. 49(d) is a fragmentary,typical sectional view showing bent tabs. FIG. 50(a) is a perspectiveview of another battery packet in accordance with the present inventionprovided with tabs, FIG. 50(b) is an enlarged view of a part G₂ in FIG.50(a), FIG. 50(c) is an enlarged sectional view taken on line X₂—X₂ inFIG. 50(b) and FIG. 50(d) is a fragmentary, typical sectional viewshowing bent tabs. FIG. 51 is a perspective view of assistance inexplaining a procedure for putting a battery in accordance with thepresent invention in a battery case. FIGS. 52(a), 52(b) and 52(c) areplan views of battery cases in accordance with the present invention,and FIGS. 52(d), 52(e) and 52(f) are sectional views of the batterycases shown in FIGS. 52(a), 52(b) and 52(c), respectively. FIG. 53 is atypical sectional view of a laminated sheet in accordance with thepresent invention for forming a battery case. FIGS. 54(a) and 54(b) areplan views of webs of laminated sheets unwound from rolls, respectively,and FIGS. 54(c) and 54(d) are perspective views of empty battery cases.

A laminated sheet 10 in accordance with the present invention includes aconductive layer (metal foil layer) 2. Flexible tabs 59 and 60 extendingfrom a battery contained in a flexible battery case 51 project from thebattery case 51.

The laminated sheet 10 has a construction as shown in FIG. 53. In thefollowing description, it is assumed that the laminated sheet 10 has theconstruction shown in FIG. 53.

(Outer side) Outermost layer/Barrier layer/Reinforcinglayer/Heat-adhesive resin layer (Inner side)

A metal foil, such as an aluminum foil, is used as the barrier layer 2to intercept the passage of moisture and gases through the laminatedsheet 10.

The laminated sheet 10 can be formed by laminating the component layersby dry lamination or sandwich lamination.

Generally, the battery case 51 is formed by processing the laminatedsheet 10, which will be described in detail later, by a heat-sealingmethod used for forming bags.

The battery case 51 in accordance with the present invention forcontaining a battery 50 a is formed in the shape of a pouch having sideheat-sealed parts 83 or a back heat-sealed part 84, such as a pouchhaving three sealed side parts as shown in FIGS. 52(a) and 52(d), apouch having four sealed side parts as shown in FIGS. 42(b) and 52(e) ora pillow type pouch as shown in FIGS. 52(c) and 52(f).

The battery case in accordance with the present invention may be any oneof those pouches.

FIGS. 52(d), 52(e) and 52(f) are sectional views taken on line X₃—X₃ inFIG. 52(a), on line X₄—X₄ in FIG. 52(b) and on line X₅—X₅ in FIG. 52(c),respectively.

It was found through studies made to find measures capable of avoidingcontact between an edge of the conductive layer 2 exposed in an endsurface of the battery case, and the bent tabs T that any troublesattributable to the above-mentioned short circuit never occur when theedges of the conductive layer 2 are recessed behind the end edge of thelaminated sheet forming the battery case 51 from which the tabs 59 and60 project outside (hereinafter referred to “edge recession”). The edgesof the conductive layer 2 may wholly be recessed or only portions of theedges of the conductive layer 2 corresponding to the tabs 59 and 60 maybe recessed.

The battery case having such edge recession may be formed by anysuitable method. The following is an example of a method of forming thebattery case. The outermost layer (generally, a biaxially orientedplastic film) is printed, and the barrier layer (metal foil) islaminated to the printed outermost layer by a predetermined method. Aweb of the plastic film for forming the outermost layer and a web of themetal foil for forming the barrier layer are supplied from a roll of thefilm and a roll of the metal foil, respectively, the web of the plasticfilm and the web of the metal foil are laminated in a web of a primarylaminated sheet, and the web of the primary laminated sheet is taken upin a roll.

The roll of the primary laminated sheet is punched by a rotary diecutter in a predetermined shape and a predetermined size to form cuts(edge recessions) 82 as shown in FIG. 54(a) or 54(b), and the web of thepunched primary laminated sheet is taken up in a roll.

When it is desired to form an edge recession along the entire length ofthe edge, the cuts 82 are formed so as to extend in the moving directionof the web of the primary laminated sheet as shown in FIG. 54(a) and,therefore, there is no possibility that the web of the primary laminatedsheet is broken.

When it is desired to form edge recessions only in portions of the edgecorresponding to the tabs, the cuts 82 are formed so as to extend acrossthe moving direction of the web of the primary laminated sheet as shownin FIG. 54(b).

Subsequently, the web of the primary laminated sheet provided with thecuts 82 is unwound from the roll, and then the reinforcing layer 1 c andthe heat-adhesive resin layer 3 are laminated in that order to thebarrier layer 2 to complete a laminated sheet.

The cuts 82 are formed by die cutting in a shape and a size suitable forforming the edge recessions.

The laminated sheet shown in FIG. 54(a) has sections for forming batterycases having three sealed sides arranged in a single longitudinal row.Each section of the laminated sheet shown in FIG. 54(a) is folded alonga folding line M to form a battery case having three sealed sides. Thelaminated sheet shown in FIG. 54(b) has sections for forming pillow typebattery cases arranged in two longitudinal rows, i.e., one rowsdemarcated by cutting lines BC3 and BC4, and the other row demarcated bycutting lines BC5 and BC6.

As shown in FIG. 49(b) or 50(b), the laminated sheet thus formed hasparts formed by removing parts of the outermost layer and the barrierlayer, and a battery case provided with edge recessions at positionscorresponding to the tabs 59 and 60 can be formed by processing thelaminated sheet.

The shape of the edge recessions when the battery case 51 is formed byprocessing the laminated sheet is dependent on the shape of the cuts 82.An edge recession can be formed along the entire length of edge or edgerecessions can be formed only in portions of the edge corresponding tothe tabs 59 and 60.

Thus, there is no possibility for the battery case to short-circuit thetabs 59 and 60 by the conductive layer 2 of the laminated sheet 10.

Even if the tabs 59 and 60 are bent as shown in FIG. 49(d) or 50(d)while the battery packet is in use, it is scarcely possible that thetabs 59 and 60 come into contact with the recessed edge of the barrierlayer 2.

Materials for the laminated sheet for forming the battery case and theconstruction of the laminated sheet will be described hereinafter.

In most cases, the tabs 59 and 60 are formed of a metal foil, such as analuminum foil or a copper foil. As mentioned above, the tabs 59 and 60are flexible and easy to bend. The battery case 51 of the polymerbattery packet 50 is formed by processing the flexible laminated sheetprovided with a conductive layer.

The battery case 51 containing the battery 50 a is formed of a laminatedsheet 10 impermeable to moisture and corrosive gases and capable ofprotecting the battery 50 a from damage that may be caused by piecingand abrasion and the like during transportation and use.

A laminated sheet 10 formed in the construction as shown in FIG. 53 maybe used.

(Outer side) Outermost layer/Barrier layer/Reinforcinglayer/Heat-adhesive resin layer (Inner side)

These layers can be laminated by dry lamination or sandwich lamination.

Preferably, the thickness of the laminated sheet 10 is in the range of50 to 400 μm. A laminated sheet of a thickness below 50 μm is inferiorin impermeability to moisture and strength, and may possibly permitmoisture to pass through into the electrolyte. A laminated sheet of athickness exceeding 400 μm has inferior heat-sealability, increases theweight of the battery case and does not conform to a basic idea ofproviding a polymer battery packet of the least possible weight. Theeffect of a laminated sheet of a thickness exceeding 400 μm in notpermitting moisture and gases to pass through cannot be expected to beas great as its thickness.

Materials of the layers of the laminated sheet are selectivelydetermined according to desired physical properties of the laminatedsheet. The following is an example of the materials and the constructionof the laminated sheet.

(Outer side) PET/AL/PET (or Ny)/EMAA (Inner side) where PET is apolyethylene terephthalate resin, AL is aluminum (foil), Ny is a nylonresin, and EMAA is an ethylene-methacrylic acid copolymer.

The outermost layer (first base film layer) 1 a is the outer surfacelayer of a battery case. Therefore, the outermost layer 1 a must beelectrically nonconductive, must have a smooth surface, must besufficiently resistant to chemicals and abrasion, must have sufficientlyhigh tensile and piercing strength, and must be capable of protecting adevice from external, detrimental, destructive, physical and chemicalactions. Biaxially oriented films of resins, particularly, biaxiallyoriented films of PET resins are preferable materials for forming theoutermost layer 1 a. A desirable thickness of the outermost layer 1 a isin the range of 5 to 30 μm. If the thickness of the outermost layer 1 ais below 5 μm, the piercing strength of the outermost layer 1 a isinsufficient and it is highly possible that pinholes are formed in theoutermost layer 1 a. If the thickness of the outermost layer 1 a isabove 30 μm, the outermost layer 1 a will adversely affect theheat-sealability of the laminated sheet and will reduce productionefficiency.

It is preferable to form the barrier layer (metal foil layer) 2contiguously with the outermost layer 1 a. The barrier layer 2 hasbarrier property to prevent moisture and gases from permeating thebattery case. It is desirable to use a metal foil, such as an aluminumfoil, as the barrier layer 2. Desirably, an aluminum foil for formingthe barrier layer 2 has a thickness in the range of 5 to 30 μm. Aluminumfoils of a thickness below 5 μm has many pinholes and are inferior inbarrier property. Aluminum foils of a thickness above 30 μm affectadversely to the production of the battery case. When a battery case isformed of a laminated sheet provided with a metal foil, such as analuminum foil, it is possible that tabs 59 and 60 are short-circuited byan exposed edge of the conductive metal foil. Although troublesincluding short circuit can be avoided if the barrier layer 2 is formedof a nonconductive material, the use of such a material inevitablyentails reduction in the barrier property of the laminated sheet.

It is preferable to form the reinforcing layer (third base film layer) 1c on the inner surface of the barrier layer 2 to reinforce the strengthof a battery case 51 formed by processing the laminated sheet. It isparticularly desirable to reinforce a battery case against the damagingactions of sharp projections. The reinforcing layer 1 c may be abiaxially oriented resin film, preferably, a biaxially orientedpolyethylene terephthalate or nylon film. Desirably, the reinforcinglayer 1 c has a thickness in the range of 5 to 30 μm. The reinforcinglayer 1 c is inferior in resistance to the piercing action of a battery50 a contained in the battery case, pinholes are liable to be formed inthe reinforcing layer 1 c if its thickness is below 5 μm. Thereinforcing layer 1 c will adversely affect the sealability of thelaminated sheet if its thickness is above 30 μm.

The innermost layer of the laminated sheet 10 forming the battery case51 is a heat-adhesive resin layer 3. Necessary parts of theheat-adhesive resin layer 3 are bonded together by heat-sealing whenforming the battery case 51. As mentioned above, it is desirable, inview of facility in operation and sealing capability, to form thebattery case by processing the laminated sheet by a heat-sealing method.When the battery case 51 is formed by a heat-sealing method, theheat-adhesive resin layer 3 is formed of a heat-adhesive material. Theheat-adhesive material must be heat-adhesive to itself and to the metalfoils forming the tabs 59 and 60. Desirable materials for forming theheat-adhesive layer 3 are polyolefin copolymers includingethylene-acrylic acid resins (EAA), ethylene-methacrylic acid resins(EMAA), ethylene-ethylacrylate resins (EEA) and ionomers.

The heat-adhesive resin layer 3 may be formed either by laminating afilm of one of the foregoing resins to the reinforcing layer 1 c or bymelting and extruding one of the foregoing resins over the surface ofthe reinforcing layer 1 c by an extruder.

Desirably, the thickness of the heat-adhesive resin layer 3 is in therange of 10 to 100 μm. If the thickness of the heat-adhesive resin layer3 is below 10 μm, the piercing strength of the heat-adhesive resin layer3 is insufficient and it is highly possible that pinholes are formed inthe heat-adhesive resin layer 3. If the thickness of the heat-adhesiveresin layer 3 is greater than 100 μm, a heat-sealing operation forforming the battery case 51 takes much time and reduces productionefficiency.

As mentioned above, the outermost layer 1 a, the barrier layer 2, thereinforcing layer 1 c and the heat-adhesive resin layer 3 may belaminated by dry lamination using a polyurethane adhesive or by sandwichlamination in which adhesive resin are extruded between the adjacentlayers.

EXAMPLES

A thin battery packet (electric device) in accordance with the presentinvention was fabricated.

Tabs: Aluminum foil (50 μm thick)

Case: Pillow type pouch

Laminated sheet:

Outermost layer: Biaxially oriented polyester film (12 μm thick)

Barrier layer: Aluminum foil (12 μm thick)

Reinforcing layer: Biaxially oriented nylon film (20 μm thick)

Heat-adhesive resin layer: Ethylene-methylacrylate (EMA) (60 μm thick)

The outermost layer the barrier layer, the reinforcing layer and theheat-adhesive resin layer were laminated by a dry lamination methodusing a two-component adhesive.

Edge recession: (1) Entire edge, Recession of 2 mm

(2) Parts of edge, Recession of 3 mm

Tabs: 7 mm wide (Width of edge recessions: 10 mm)

The tabs extending outside the battery case were bent for short circuittesting. There was no possibility at all that the tabs come into contactwith the edge of the conductive layer of the battery case.

The battery case of the present invention capable of preventing contactbetween the tabs and the conductive layer is applicable for containingvarious electric devices.

Thirteenth Embodiment

A thirteenth embodiment according to the present invention will bedescribed with reference to FIGS. 55 to 57, in which parts like orcorresponding to those of the first embodiment are designated by thesame reference characters and the description thereof will be omitted.

FIG. 55(a) is a perspective view of a battery packet in accordance withthe present invention, FIG. 55(b) is an enlarged view of a part G₁ inFIG. 55(a), FIG. 55(c) is an enlarged sectional view taken on line X₁—X₁in FIG. 55(b). FIG. 56 is a perspective view of assistance in explaininga procedure for putting a battery in accordance with the presentinvention in a case. FIGS. 57(a) and 57(b) are perspective views of tabscoated with insulating film layers in different manners, respectively.

A battery packet in accordance with the present invention comprises abattery 50 a provided with flexible tabs 59 and 60 extending therefrom,and a flexible case 51 formed of a laminated sheet 10 having aconductive layer 2 and containing the battery 50 a so that the tabs 59and 60 extend through a heat-sealed part 94. The case 51 has aconstruction capable of preventing the tabs 59 and 60 from beingshort-circuited by the conductive layer 2 of the laminated sheet 10.

In most cases, the tabs 59 and 60 are formed of a metal foil, such as acopper foil and are flexible and easy to bend. The case 51 of thebattery packet 50 is flexible and has a conductive layer. In aconventional battery packet 50, tabs 59 and 60 are very close to an endedge of a case 51. Therefore it is possible that the tabs 59 and 60 comeinto contact with an exposed edge of a conductive layer included in alaminated sheet 10 forming the case 51 when the tabs 59 and 60 are bent.If the tabs 59 and 60 come into contact with the edge of the conductivelayer, the battery packet 50 does not function normally, and troublesmay possibly occur. It is possible that a battery included in thebattery packet is caused to discharge and to reduce electric energystored therein and, in the worst case, the battery is exhausted and isunable to function.

The inventors of the present invention made earnest studies to solvesuch a problem and found that any troubles attributable to theabove-mentioned short circuit never occur when each of the tabs 59 and60 excluding a contact part 93 is coated with an insulating film layer92 as shown in FIG. 55. More specifically, each of the tabs 59 and 60 ofthe battery packet of the present invention is covered with aninsulating film layer 92 in a desired shape as shown in FIG. 57(a) or57(b). Suitable materials for forming the insulating film layer 92 arehot-melt resins containing an acid-denatured polyolefin resin as aprincipal component, epoxy resins, polyimide resins, reactive acrylicresins and elastomers.

Short-circuiting of electrodes by a component of a case formed of aconventional laminated sheet occurs because tabs are very close to anedge of the conductive layer of the laminated sheet, and flexible andeasy to bend. The present invention has been made on the basis of afinding that such a short-circuit trouble can be prevented by coating apredetermined part of each tab, including the boundary between the endedge of the case and the tab with an insulating film in a predeterminedshape.

It is desirable that the insulating film 92 has an insulation resistanceof 10¹³ Ω or above.

Various materials for forming such an insulating film were examined andit was found that suitable materials for forming such an insulating filmare hot-melt acid-denatured polyolefin coating materials containing anacid-denatured polyolefin resin as a principal component, epoxy resins,polyimide resins, reactive acrylic resins and elastomers.

More specifically, hot-melt acid-denatured polyolefin coating materialsare ethylene-acrylic acid resins (EAA), ethylene-methacrylic acid resins(EMAA), ethylene-ethylacrylate resins (EEA) and ionomers.

The tab can be coated with an insulating film of a hot-meltacid-denatured polyolefin coating material by a nozzle coating method, aroller coating method, a slot coating method, spray coating method, amelt-blown coating method, a wheel coating method or a screen coatingmethod. The insulating film may be formed on the tabs after attachingthe tab to the battery 50 a, on a metal foil before the metal foil ispunched or cut into the tabs. The insulating film may be formed byapplying the hot-melt acid-denatured polyolefin resin to predeterminedparts of the tabs 59 and 60 by a hot-melt applicator before putting thebattery 50 a into a case.

The hot-melt acid-denatured polyolefin resin may be applied topredetermined parts of a web of metal foil for forming the tabs 59 and60 by a gravure coating method or a roller coating method, the web maybe cut or punched into tabs 59 and 60 of a predetermined size, and thetabs 59 and 60 may be bonded to a principal part C.

The insulating film 92 is formed on a part of the tab 59 (60) extendingon the outer and the inner side of the end edge of the case 51 fromwhich the tab 59 (60) projects outside. Suppose that a boundary line Mshown in FIG. 57 corresponds to the end edge of the case 51, theinsulating film 92 is formed so as to extend in a predetermined lengthon each of the opposite sides of the boundary line M. The length is notless than the thickness of the laminated sheet 10 and may be a lengthgreat enough to prevent short circuit even if the tabs 59 and 60 arebent.

The insulating film 92 is formed so as to cover both the surfaces of thetabs 59 and 60. If necessary, the side surfaces of the tabs 59 and 60,as well as both the surfaces of the same, may be coated with theinsulating film 62 as shown in FIG. 57(b).

The battery 50 a is inserted in the case 51, and a part of the case 51corresponding to the boundary line M shown in FIG. 57(a) or 57(b) issealed. Preferably, the part of the case 51 is sealed by a heat-sealingmethod so that the sealant layer 3 serving as the innermost layer of thelaminated sheet 10 forming the case 51 is bonded to the insulating films92 partly coating the tabs 59 and 60, and parts of the tabs 59 and 60not coated with the insulating film 92.

The insulating films 92 coating the tabs 59 and 60 may be those of ahot-melt acid-denatured polyolefin coating material, an epoxy resin, apolyimide resin, a reactive acrylic resin or an elastomer.

An epoxy resin, a polyimide resin, a reactive acrylic resin or anelastomer for forming the insulating film 92 may be applied topredetermined parts of a web of a material for forming the tabs 59 and60 by a gravure printing method, a gravure-offset printing method, aletterpress printing method, an offset printing method or a silk-screenprinting method.

The position and area of the insulating film 92 formed of an epoxyresin, a polyimide resin, a reactive acrylic resin or an elastomer arethe same as those of the insulating film 92 formed of a hot-meltacid-denatured polyolefin resin.

EXAMPLES Example 1

Device: Flat battery packet

Case: Pillow type pouch

Laminated sheet: PET/AL/ON/LLDPE

Tabs: Aluminum foil (50 μm thick)

Insulating film: Acid-denatured polyolefin resin

(PURIMAKORU commercially available from Dau Kemikaru Nippon K.K.) wasspread in a 30 μm thick film by a hot-melt applicator.

Shape of insulating film: The insulating film of 16 mm in length wasformed so as to cover both the surfaces of a part of 8 mm in length ofeach tab extending outside the case from the end edge of the case, andboth the surfaces of another part of 8 mm in length of the tab extendinginside the case from the end edge of the case.

Coating method: The tabs were coated with the insulating films by ahot-melt applicator after attaching the same to a main part of thedevice.

The flat battery packet was subjected to a short circuit test in whichthe tabs extending from the end edge of the case were bent forcibly tobring the same into contact with the edge of the conductive layerexposed in the end edge of the case. Short circuit did not occur and thereliable function of the insulating films was verified.

Incidentally, a flat battery packet in a comparative example wasfabricated under the same conditions as those under which the foregoingexample was fabricated, excluding that tabs were not coated with anyinsulating films, and the flat battery packet in the comparative examplewas subjected to the same short circuit test. Short circuit occurred inthe flat battery packet in the comparative example.

The electrode structure in accordance with the present inventioneliminates the possibility of the tabs coming into contact with theconductive layer of the case. The electrode structure in accordance withthe present invention is applicable to the tabs of various devices.

Fourteenth Embodiment

A fourteenth embodiment according to the present invention will bedescribed with reference to FIGS. 58 to 60, in which parts like orcorresponding to those of the first embodiment are designated by thesame reference characters and the description thereof will be omitted.

A polymer battery packet in accordance with the present inventiondescribed herein is illustrative and not restrictive and many changesare possible therein without departing from the scope of the presentinvention.

FIG. 58(a) is a perspective view of a battery packet in accordance withthe present invention, FIG. 58(b) is an enlarged view of a part G₁ inFIG. 58(a), FIG. 58(c) is an enlarged sectional view taken on line X₁—X₁in FIG. 58(b). FIG. 59 is a perspective view of assistance in explaininga procedure for putting a battery in accordance with the presentinvention in a case.

FIGS. 60(a), 60(b) and 60(c) are perspective views of tabs coated withinsulating film layers in different manners, respectively.

Referring to FIGS. 58(a), 58(b) and 58(c), a battery packet 50 has aflexible case 51 formed of a laminated sheet 10 (FIG. 53) having aconductive layer 2 formed of a conductive material, a battery 50 acontained in the case 51, and flexible tabs 59 and 60, i.e., electrodes,extending from the battery 50 a contained in the case 51. A part of eachof the tabs 59 and 60 extending outside from a sealed end edge of thecase 51 excluding a contact part 93 is covered with a heat-adhesiveinsulating film (insulating cover) 92 to prevent the tabs 59 and 60 fromcoming into contact with and being short-circuited by the conductivelayer 2 of the laminated sheet 10. The case 51 is formed by rolling thelaminated sheet 10 in a tubular structure, and heat sealing the oppositeend parts of the tubular structure in end heat-sealed parts 94 and thejoint of the side edge parts of the laminated sheet 10 in a backheat-sealed part 95.

In most cases, the tabs 59 and 60 of an electrode structure inaccordance with the present invention are formed of a metal foil, suchas a copper foil and a flexible and easy to bend. The case 51 is formedby processing the flexible laminated sheet 10 including a conductivelayer 2, such as a metal foil. Parts of the tabs 59 and 60 extendingoutside the case 51 are very close to the conductive layer 2 of thelaminated sheet 10 forming the case 51. Therefore, it is possible thatthe tabs 59 and 60 come into contact with an exposed edge of theconductive layer 2 of the laminated sheet 10 when the tabs 59 and 60 arebent. If the tabs 59 and 60 come into contact with the edge of theconductive layer 2, the battery packet 50 does not function normally,and troubles may possibly occur. It is possible that the battery of thebattery packet 50 is caused to discharge and to reduce electric energystored therein and, in the worst case, the battery is exhausted and isunable to function.

The inventors of the present invention made earnest studies to solvesuch a problem and found that any troubles attributable to theabove-mentioned short circuit never occur when parts of the tabs 59 and60 extending outside from the case 51 and adjacent to the end edge ofthe case 51 are coated with insulating film layers 92 as shown in FIG.58.

The tabs 59 and 60 of the electrode structure in accordance with thepresent invention are flexible foils of copper, aluminum, tin, gold,silver or an alloy of some of those metals.

The present invention has been made on the basis of a finding that sucha short-circuit trouble can be prevented by coating parts of apredetermined area of the tabs 59 and 60 extending outside from the case51 and including the boundary between the end edge of the case 51 andthe tabs 59 and 60 with insulating films 92. The parts of apredetermined area of the tabs 59 and 60 are those possible to come intocontact with the exposed edge of the conductive layer 2 of the case 51and extending outside and inside the case 51 from a boundary line Mcorresponding to the end edge of the case 51 in a length in the range ofabout 5 to about 20 mm. The area of the parts of the tabs 59 and 60 mayproperly be determined taking into consideration the thickness of thelaminated sheet 10 forming the case 51 and the flexibility of the tabs59 and 60. As shown in FIG. 58(a), free end parts or parts near the freeends of the tabs 59 and 60 are not coated with the insulating film touse the same as contact parts 93.

The contact parts 93 need not necessarily be formed in a rectangularshape; the part extending outside the case 51 of each of the tabs 59 and60 may entirely be coated with the insulating sheets 92 provided with apunched round hole at a position corresponding to an end part of each ofthe parts of the tabs 59 and 60, and a part of each of the tabs 59 and60 exposed in the round hole may be used as a contact part.

The adhesive insulating film for the electrode structure in accordancewith the present invention will be described.

The adhesive insulating film 92 for the electrode structure inaccordance with the present invention is bondable to the tabs 59 and 60,and the innermost layer 3 of the case 51 by heat-sealing. When wrappingthe adhesive insulating film 92 around and bonding the same byheat-sealing to the part of the tab 59 (60) contiguous with the end edgeof the case 51, the adhesive insulating film 92 can be bonded to boththe tab 59 (60) and the innermost layer 3 of the case 51. Therefore, thebattery 50 a can satisfactorily be sealed hermetically in the case 51.Suitable materials for forming the insulating film 92 meeting theforegoing requirements are acid-denatured polyolefin resins includingethylene-acrylic acid resins (EAA), ethylene-methacrylic acid resins(EMAA), ethylene-ethylacrylate resins (EEA) and ionomers.

When the tab 59 (60) is connected to the battery 50 a, the tab 59 (60)can be coated with the insulating films 92 of a predetermined area byputting insulating films 92 on both the surfaces of the tab 59 (60) asshown in FIG. 60(a) and applying pressure and heat to the insulatingfilms 92. Thus, parts of the tab 59 (60) respectively extending on theopposite sides of the boundary line M corresponding to the end edge ofthe case 51 are coated with the insulating films 92.

The battery 50 a is inserted in the case 51, and the end edge part ofthe case 51 is heat-sealed hermetically so as to sandwich the tabs 59and 60 between the walls of the case 51.

The side surfaces of the necessary parts of the tabs 59 and 60, as wellas both the surfaces of the same, may be coated with the insulating film62 as shown in FIG. 60(b) or the necessary parts of the tabs 59 and 60may be sandwiched between insulating films 92 of a length greater thanthe width of the tabs 59 and 60 as shown in FIG. 60(c). FIGS. 60(e),60(f) and 60(g) are sectional views taken on lines X₂—X₂, X₃—X₃ andX₄—X₄ in FIGS. 60(a), 60(b) and 60(c), respectively.

It is also possible to bond insulating tapes to a web of a metal foilunwound from a roll, to cut the web into tabs as shown in FIG. 60(a),and to connect the tabs to the battery. The battery 50 a thus providedwith the tabs may be inserted in the case 51 and the open end of thecase 51 may be heat-sealed to seal the battery 50 a in the case 51.

As mentioned above, the insulating film 92 is formed of anacid-dematired polyolefin resin which is highly adhesive to both thetabs 59 and 60 of a metal foil or the like, and a highlywater- andmoisture-proof polyolefin resin, such as a polyethylene resin.Generally, the innermost layer 3 of the case 51 is formed of anacid-denatured resin only in view of securing heat-adhesion to metalfoils or the like. According to the present invention, both the tabs 59and 60 and the insulating sheet 92 can surely be bonded to the innermostlayer 3 of the case 51, and the end surface of the acid-denaturedpolyolefin resin layer is exposed in only portions of the end surface ofthe case corresponding to the tabs 59 and 60 projecting from the case,when only the insulating film 92 is formed of the acid-denaturedpolyolefin resin, and the sealant layer of a polyolefin resin takes mostpart of the end surface. Accordingly, the case has an improvedmoisture-proof ability and is capable of maintaining the ability of theelectric device for a long period.

EXAMPLES

Device: Battery packet

Case: Pillow type pouch

Laminated sheet: PET (12 μm thick)/AL (40 μm thick)/ON (25 μm thick)/CPP(70 μm thick)

Adhesive insulating film: EMAA (30 μm thick) Tabs: Copper foil (50 μmthick)

Aluminum foil (50 μm)

The flat battery packet was subjected to a short circuit test in whichthe tabs extending from the end edge of the case were bent forcibly tobring the same into contact with the edge of the conductive layerexposed in the end edge of the case. Short circuit did not occur and thereliable function of the insulating films was verified.

Incidentally, a battery packet in a comparative example was fabricatedunder the same conditions as those under which the foregoing example wasfabricated, excluding that tabs were not coated with any insulatingfilms, and the battery packet in the comparative example was subjectedto the same short circuit test. Short circuit occurred in the batterypacket in the comparative example.

The electrode structure in accordance with the present inventioneliminates the possibility of the tabs coming into contact with theconductive layer of the case. The construction of the battery packet inaccordance with the present invention is applicable to various electricdevices.

The innermost layer of the case can be formed of a polyolefin resin whenthe insulating film is formed of an acid-denatured polyolefin resin.Consequently, the case for electric devices has improved water- andmoisture-proof properties, the case is impermeable to moisture and thedeterioration of the ability of the electric device can be prevented.

Fifteenth Embodiment

A fifteenth embodiment according to the present invention will bedescribed with reference to FIGS. 61 to 64, in which parts like orcorresponding to those of the first embodiment are designated by thesame reference characters and the description thereof will be omitted.designated by the same reference characters and the description thereofwill be omitted.

A battery packet in accordance with the present invention has aconstruction capable of preventing tabs extending from a batterycontained in a soft case formed of a laminated sheet including aconductive material from coming into contact with the conductivematerial of the laminated sheet and from being short-circuited by theconductive material.

FIG. 61(a) is a perspective view of a battery packet in accordance withthe present invention, FIG. 61(b) is a perspective view of a battery anda case for containing the battery, and FIG. 61(c) is a development ofthe case. FIG. 62(a) is a sectional view taken on line X₁—X₁ in FIG.61(a) and FIG. 62(b) is a sectional view taken on line X₂—X₂ in FIG.61(a). FIG. 63 is an enlarged view of a part Y in FIG. 62(a). FIGS.64(a), 64(b) and 64(c) are plan views of cases in accordance with thepresent invention, and FIGS. 64(d), 64(e) and 64(f) are sectional viewstaken on lines X₂—X₂, X₃—X₃ and X₄—X₄ in FIGS. 64(a), 64(b) and 64(c),respectively.

Referring to FIG. 61, a battery packet has a case 51 provided withopenings 96 at predetermined positions, and a battery 50 a sealed in thecase 51. Parts of tabs 59 and 60 exposed in the openings 96 serve ascontact parts. Embodiments of the present invention will be describedhereinafter with reference to the drawings. The present invention is notlimited in its practical application to the embodiments specificallydescribed below and changes may be made therein without departing fromthe scope of the invention.

In most cases, the case 51 of the battery packet in accordance with thepresent invention is formed of laminated sheet 10 formed by laminatinglayers of different materials. The laminated sheet 10 may be providedwith a layer of a conductive material to protect a device from piercingand abrading actions, and chemical changes which may be caused bymoisture and corrosive gases.

The case 51 in accordance with the present invention is formed, in mostcases, by processing the laminated sheet 10 shown in FIG. 53 by aheat-sealing method in the shape of a pouch having sealed endheat-sealed parts 94 and a back heat-sealed part 95. More specifically,the case 51 may be a pouch having three sealed sides as shown in FIGS.52(a) and 52(d), a pouch having four sealed sides as shown in FIGS.52(b) and 52(d) or a pillow type pouch as shown in FIGS. 52(c) and52(f). In the following description, the case 51 is assumed to be apillow type pouch.

The battery packet 50 in accordance with the present invention is formedby inserting the battery 50 a provided with the tabs 59 and 60 in thecase 51 and heat-sealing an open end part of the case 51. The case 51containing the battery 50 a is provided with the openings 96 of apredetermined size at positions corresponding to parts of the tabs 59and 60 connected to the battery 50 a. When the open end part of the case51 is sealed, the openings 96 corresponds to the contact parts of thetabs 59 and 60, respectively. The openings 96 may be formed at twopositions on the laminated sheet 10 to form two contact parts on oneside of the tab 59 and one side of the tab 60, respectively, or may beformed at four positions on the laminated sheet 10 as shown in FIGS.61(b) and 61(c) to form four contact parts on both sides of the tab 59and both sides of the tab 60, and two contact parts, respectively. Thebattery 50 a is inserted in the case 51, the open end part of the case51 through which the tabs 59 and 60 extend outside is sealedhermetically to complete the battery packet 50. The open end part of thecase 51 is sealed after evacuating the case 51 or reducing the pressurein the case 51 to make the case 51 come into close contact with thebattery 50 a in order that the battery packet 50 can be used withfacility. As mentioned above, a sealant layer 3 of an acid-denaturedpolyolefin resin included in the laminated sheet 10 forming the case 51is adhesive to the tabs 59 and 60. Therefore, moisture and gases areunable to penetrate into the case 51 through the brims of the contactparts, and hence the battery 50 a can be kept in a satisfactorycondition for a long time.

Preferably, the openings 96 of the case 51 are formed in the laminatedsheet 10 by a punching machine using a die set before shaping the samein the case 51. The battery packet 50 in accordance with the presentinvention is fabricated by forming the case 51 by a bag forming processusing a bag forming machine, and inserting and sealing the battery 50 ain the case 51 by another process, or by forming the case 51, insertingthe battery 50 a in the case 51 and sealing the case by a single processof an automatic packaging system. In either case, the laminated sheet 10is supplied in a web unwound from a roll of the laminated sheet 10.Resister marks (eye marks) are printed on the web of the laminated sheetwhen printing necessary matters on the web, the eye marks are detectedby a photoelectric device and the tension of the web is controlled toform the openings 96 at correct positions.

The sealant layer 3 of an acid-denatured polyolefin resin included inthe laminated sheet 10 forming the case 51 is ensures the bonding of theinner surface of the case 51 by heat-sealing, and the bonding of thecase 51 to the tabs 59 and 60. Accordingly, the tabs 59 and 60 can befixed to the case 51 and, consequently, the tabs 59 and 60 will noteasily be bent and there is no possibility that the tabs 59 and 60 comeinto contact with an edge of the conductive layer exposed on an end edgeof the case 51.

Parts of the tabs 59 and 60 of the battery packet 50 in accordance withthe present invention are exposed as shown in FIG. 63 to form contactparts 5 to be brought into contact with the electrodes of a device whichuses the battery packet 50. Since the laminated sheet 10 forming thecase 51 is bonded by heat-sealing to the tabs 59 and 60 so as to coverthe tabs 59 and 60 entirely, excluding the contact parts, the tabs 59and 60 covered with the laminated sheet 10 are rigid as compared withthe bare metal foil forming the tabs 59 and 60, the tabs 59 and 60 willnot easily be bent, and there is no possibility that the tabs 59 and 60come into contact with an exposed edge of a conductive layer 2 includedin the laminated sheet 10.

EXAMPLE

A battery packet was fabricated by inserting and sealing a flat batteryprovided with tabs of a 300 μm thick cooper foil in a case.

Flat battery: 50 mm×500 mm×2 mm

Tabs: 100 mm wide, 20 mm long, 200 μm thick, Two tabs extended from oneend of the battery

Case:

Laminated sheet: (Outer side) PET (12 μm thick)/AL (40 μm thick)/ONy (25μm thick)/EAA (70 μm thick) (Inner side)

Pillow type pouch of 75 mm in width and 130 mm in length withheat-sealed end parts and heat-sealed back part of 7 mm in width

Four openings were formed in the laminated sheet before shaping thelaminated sheet in a pouch to form contact parts on both surfaces ofeach of the tabs.

Assembly: The flat battery was inserted in the case, and the open endpart of the case was pressed and heated for two seconds with a hot plateheated at 210° C. to heat-seal the case and to bond the case to the tabsso that the tabs excluding the contact parts are covered entirely withthe case.

The tabs covered with the case were bent forcibly for short circuittesting. The tabs could not be brought into contact with an edge of analuminum foil exposed on an edge of the case.

In the battery packet in accordance with the present invention, there isno possibility that the tabs are shorted by the conductive layer of thecase. Since the tabs excluding their contact parts are covered entirelywith the laminated sheet forming the case, the tabs thus covered arerigid and able to serve as stable electrodes.

Sixteenth Embodiment

A sixteenth embodiment according to the present invention will bedescribed with reference to FIGS. 65 to 69, in which parts like orcorresponding to those of the first embodiment are designated by thesame reference characters and the description thereof will be omitted.

FIG. 65(a) is a perspective view of a battery packet in accordance withthe present invention, FIG. 65(b) is an enlarged view taken in thedirection of the arrow G₁ in FIG. 65(a), and FIG. 65(c) is an enlargesectional view taken on line X₁—X₁ in FIG. 65(b). FIG. 66(a) is aperspective view of a battery and a case having an open end part forcontaining the battery, and FIG. 66(b) is a sectional view taken on lineX₂—X₂ in FIG. 66(a). FIG. 67 is a perspective view of a case inaccordance with the present invention, and FIG. 68 is a perspective viewof another case in accordance with the present invention.

Referring to FIGS. 65(a), 65(b) and 65(c), a battery 50 a is inserted ina flexible case 51 formed by processing a laminated sheet 10 (FIG. 53)including a conductive layer formed of a conductive material, andflexible tabs 59 and 60 extending from the battery 50 a project outsidefrom the case 51. Parts of an end edge of the case 51 through which thetabs 59 and 60 project outside is covered with covering sheets 102 toprevent short-circuiting the tabs 59 and 60 by the conductive layer 2 ofthe laminated sheet 10.

In most cases, the tabs 59 and 60 are formed of a metal foil, such as acopper foil and hence are flexible and easy to bend. The case 51 isformed by folding the laminated sheet 10 having the conductive layer 2of a metal foil or the like and forming heat-sealed parts 94 and a backheat-sealed part 95. The tabs 59 and 60 extending outside from the case51 are very close to the edge of the conductive layer 2 of the laminatedsheet 10 forming the case 51. Therefore, it is possible that the tabs 59and 60 come into contact with the edge of the conductive layer 2 of thelaminated sheet 10 exposed on the end edge of the case 51 if the tabs 59and 60 are bent. If the tabs 59 and 60 come into contact with the edgeof the conductive layer 2, the battery packet 50 does not functionnormally, and troubles may possibly occur. It is possible that thebattery of the battery packet 50 is caused to discharge and to reduceelectric energy stored therein and, in the worst case, the battery isexhausted and is unable to function.

The inventors of the present invention made earnest studies to solvesuch a problem and found that any troubles attributable to theabove-mentioned short circuit never occur when the parts of the end edgeof the case 51 through which the tabs 59 and 60 project outside arecovered with the covering sheets 102 and the present invention has beenmade on the basis of such findings.

The shape of the case 51 of the battery packet 50 and the laminatedsheet forming the case 51 will be described.

The case 51 of the battery packet 50 has the shape of a pouch formed byprocessing the laminated sheet 10 by a heat-sealing method.

The insulating covering sheets 102 for covering parts of the end edge ofthe case 51 formed by heat-sealing an open end part 98 will bedescribed.

Parts of the end edge of the case 51 respectively corresponding to thetabs 59 and 60 may be covered individually with covering sheets 102 of awidth nearly equal to that of the tabs 59 and 60 as shown in FIG. 67, oreach of parts of the end edge of the case 51 corresponding to the twotabs 59 and 60 may be covered with a single covering sheet 102 of awidth corresponding to that of the part of the end edge corresponding tothe two tabs 59 and 60 as shown in FIG. 68.

The covering sheet 102 has at least an outer layer formed of anonconductive material and an inner layer formed of a material which canbe bonded to the case 51 and does not come off the case 51 for a longtime. The covering sheet 102 may be bonded to the case 51 with anadhesive or by a heat-sealing method. As mentioned above, it is generalto form the outermost layer 1 a of the laminated sheet 10 forming thecase 51 of a film which is scarcely heat-sealable, such as a biaxiallyoriented polyethylene terephthalate film, and hence the case must beprovided with a heat-adhesive layer on its outer surface to bond thecovering sheets 102 by a heat-sealing method to the case 51. Preferably,a tape produced by coating an insulating base film with an adhesiveresin (hereinafter referred to as “adhesive tape”) is used as thecovering sheet 102 in accordance with the present invention.

Desirably an adhesive tape, i.e., a laminated sheet, to be used as thecovering sheet 102 has an insulating base layer 102 a havingsatisfactory elasticity. Suitable materials for forming the base layerof the covering sheet 102 are a biaxially oriented film of polyethyleneterephthalate resin, and films of nylon resins, polycarbonate resins,polyethylene resins, polypropylene resins, polyvinyl chloride resins,polyvinylidene chloride resins, Teflon® and the like. Uniaxxially orbiaxially oriented films of those materials are more preferable (FIG.69).

An adhesive for forming an adhesive layer 102 b included in the adhesivetape may be selected out of rubber, synthetic rubbers and siliconerubbers taking into consideration the adhesiveness of the adhesive tothe case. The surface of the base layer may be finished by awater-repellent finishing using silicone or the like.

The covering sheets 102 may be attached to the case 51 formed in theshape of a pouch so as to cover the parts of the end edge part of thecase 51 corresponding to the tabs 59 and 60 before sealing the open endpart 98 of the case 51 or may be attached to parts of the laminatedsheet 10 corresponding to the parts of the case 51 through which thetabs 59 and 60 extend, and then the laminated sheet 10 may be shaped inthe case 51.

The covering sheets 102 must have a width greater than that of the tabs59 and 60. It is preferable, in view of reducing the possibility ofcontact between the tabs 59 and 60 with the conductive layer of the case51, to use the covering sheet 102 of a width corresponding to the widthof a region of the end edge of the case 51 including the two tabs 59 and60.

The covering sheet 102 has an inner part of a length n₁ lying on theinner surface of the case 51 and an outer part of a length n₂ lying onthe outer surface of the case 51. The lengths n₁ and n₂ are great enoughif the covering sheet 102 does not come off the case 51. Basically, theinner part of the length n₁ of the covering sheet 102 need not perfectlybe bonded to the tabs 59 and 60. The length n₁ must be smaller than thewidth of the heat-sealed part 94.

EXAMPLE

Device: Flat battery packet of 50 mm×100 mm×3.5 mm

Case: PET (12 μm thick)/AL (40 μm thick)/ONy (25 μm thick)/EAA (70 μmthick)

Tabs: Copper foil, 30 μm thick, 14 mm wide, 45 mm long

Two tabs extended from an end of the main part of the battery packet

Covering sheet: Polyethylene terephthalate resin film (25 μm thick) andurethane adhesive layer (20 mm thick).

In the battery packet, there is no possibility that the tabs come intocontact with the conductive layer of the case. The construction of thisbattery packet is applicable to various devices.

Seventeenth Embodiment

A seventeen embodiment of the present invention will be described withreference to FIGS. 70 and 71. Referring to FIGS. 70 and 71, an adhesivesheet 112 is folded in two leaves along a folding line 117, and tabs 59and 60 are sandwiched between the two leaves of the adhesive sheet 112.As shown in FIG. 71(a), the adhesive sheet 112 is folded along thefolding line 117 in two symmetrical leaves. The adhesive sheet 112 isprovided with openings 113 at positions corresponding to contact partsof tabs 59 and 60. As shown in FIG. 70(b), the tabs 59 and 60 aresandwiched between the two leaves of the folded adhesive sheet 112, andparts of the adhesive surfaces of the leaves of the adhesive sheet 112other than those corresponding to the tabs 59 and 60 are bondedtogether. A battery 50 a is inserted in a case 51, and open end parts ofthe case 51 are sealed in sealed parts 94 to complete a battery packet50 as shown in FIG. 70(a).

As shown in FIG. 71(b), the adhesive sheet 112 comprises a base layer112 a and an adhesive layer 112 b. The base layer 112 a is a film of anonconductive material suitable for adhesive bonding, such as anoriented or nonoriented film of one of polyethylene terephthalateresins, nylon resins, vinyl chloride resins, vinylidene chloride resins,polyethylene resins, polypropylene resins, Teflon® and the like.

As mentioned above, when fabricating the battery packet in accordancewith the present invention, the open end part of the case is sealed withthe adhesive sheet 112 sandwiched between the end edge parts of theopposite walls of the case 51. It is desirable that the sealant layer 3of a laminated sheet 10 forming the case 51 is welded to the base layer112 a of the adhesive sheet 112. If the base layer 112 a of the adhesivesheet 112 is a biaxially oriented polyethylene terephthalate film, it isdifficult to bond together the sealant layer 3 of the laminated sheet 10forming the case 51, and the adhesive sheet 112 by heat-sealing. Asecondary adhesive layer 112c capable of being easily bonded to thesealant layer 3 of the laminated sheet 10 forming the case 51 may beformed on the surface layer 112 a of the adhesive sheet 112 as shown inFIG. 71(c). The secondary adhesive layer 112 c may be formed of a resinof the same kind as that forming the sealant layer 3 of the case 51. Theadhesive layer 112 b of the adhesive sheet 112 is formed of a highlyheat-resistant material capable of firmly adhering to the tabs 59 and 60and of preventing the adhesive sheet 112 from coming off the tabs 59 and60, such as styrene-butadiene rubber, glycerol ester of hydrogenatedrosin or a petroleum hydrocarbon.

Eighteenth Embodiment

An eighteenth embodiment of the present invention will be described withreference to FIGS. 72 and 73. A case 51 in the eighteenth embodiment isformed by heat-sealing peripheral parts of a pair of laminated sheets 10in a sealed peripheral part 115 having an improved barrier property.

If oxygen and moisture are detrimental to the contents of the case 51,the laminated sheet 10 forming the case 51 is provided with a layerhaving a high barrier property.

Generally, an adhesive layer employed in adhesively bonding joints oflaminated sheets to form a packing case, such as a pouch, does not haveany barrier property, and hence oxygen and moisture penetrate theadhesive layer into the packing case to affect the contents of thepacking case adversely.

Such a problem may be solved by forming the adhesive layer of a resinhaving barrier property. However, any resins having both adhesivestrength sufficient for forming an adhesive layer and a satisfactorybarrier property are unavailable at present.

The barrier property of the adhesive layer may be improved by reducingthe thickness of the adhesive layer (heat-adhesive resin layer 3) asshown in FIG. 73(a). If the adhesive layer is excessively thin, theadhesive layer is subject to heat deterioration, the strength of theadhesive layer decreases and the case breaks.

A sealed peripheral part 115 formed by bonding together peripheral partsof a pair of laminated sheets 10 may be crimped in a wavy sectionalshape as shown in FIG. 73(b). However, when the sealed edge part iscrimped, the strength of the adhesive layer is reduced and, in somecases, the case breaks.

Studies were made to improve the barrier property of the sealed edgepart without reducing the bonding strength of the adhesive layer, and itwas found that the foregoing problem can be solved by bringing therespective barrier layers of laminated sheets forming the front and theback wall of a case close to or into contact with each other.

A case in an example will be described below with reference to thedrawings.

Peripheral parts of a pair of laminated sheets 10 each having a barrierlayer 2 and an adhesive layer 3 are bonded together to form a sealedperipheral part 115. As shown in FIG. 72(a), parts of the barrier layers2 included in the peripheral parts of the pair of laminated sheets 10can be brought close to or into contact with each other by pressing boththe pair of laminated sheets 10 to form grooves 116 in both the pair oflaminated sheets 10 so as to shove aside portions of the adhesive layers3 corresponding to the grooves 116.

As shown in FIG. 72(b), a part of the barrier layer 2 of one of the pairof laminated sheets 10 may be brought close to or into contact with thebarrier layer 2 of the other laminated sheet 10 by pressing the formerlaminated sheet 10 to form a groove 116 in the former laminated sheet10.

FIG. 72(c) shows a sealed peripheral part 115 formed by bonding togetherperipheral parts of a pair of laminated sheets 10, and provided with apinched edge part formed by pressing an edge part of the sealedperipheral part 115 so as to shove aside the adhesive layers 3 to bringthe barrier layers 2 of the pair of laminated sheets 10 close to or incontact with each other.

In a modification of the sealed peripheral part 115 shown in FIG. 72(c),a part of the barrier layer 2 of a peripheral part of one of the pair oflaminated sheets 10 may be brought close to or into contact with thebarrier layer 2 of the other laminated sheet 10 by pressing an edge partof only the former laminated sheet 10.

The parts of the barrier layers 2 of the pair of laminated sheet 10 inthe sealed peripheral part can be brought close to or into contact witheach other so as to shove aside the adhesive layers by a method using ahot plate or ultrasonic waves.

The laminated sheet forming the front or the back wall of the case maybe processed to form the groove before, after or during a sealingprocess for bonding together the pair of laminated sheets to form thecase.

The barrier layer 2 and the adhesive layer 3 are essential componentlayers of the laminated sheet. The laminated sheet may be provided withadditional layers including a strengthening layer.

Suitable materials for forming the barrier layer 2 are metal foils, suchas aluminum foils, resin films or resin sheets coated with a metal film,such as an aluminum film formed by vacuum evaporation, films or sheetsof resins having barrier property, such as saponified ethylene-vinylacetate copolymers, polyamide resins, such as an MXD nylon 6,polyacrylonitrile resins and polyvinylidene chloride resins, and resinfilms or resin sheets coated with a film of an inorganic oxide, such assilicon dioxide (SiO₂), alumina (Al₂O₃) or magnesium oxide (MgO) byvacuum evaporation.

Such a film of one of the foregoing inorganic oxide can be formed on aresin film or a resin sheet by a chemical vapor deposition method (CVDmethod), such as a plasma-assisted chemical vapor deposition method, ora physical vapor deposition method (PVD method), such as a vacuumevaporation method.

The inorganic oxide film formed by vacuum deposition may be either asingle-layer film of an inorganic oxide, such as one of silicon dioxide,alumina and the like or a laminated film having a plurality of layers ofsome of those inorganic oxides.

A multilayer film formed by using a chemical vapor deposition method anda physical vapor deposition method in combination. There is not anyrestriction on the order of forming those films by evaporation.

For example, it is possible to form a silicon dioxide film first, andthen an alumina film. The order may be reversed.

A composite film of an inorganic oxide film and a barrier film of aresin having barrier property may be formed by coating the inorganicoxide film formed by vacuum evaporation with the resin having barrierproperty.

Nineteenth Embodiment

A nineteenth embodiment according to the present invention will bedescribed with reference to FIGS. 74 and 75. It sometimes occurs that alaminated sheet manufactured by a generally used dry lamination methodand forming a case delaminates along a plane of lamination between ametal foil layer and an inner layer included in the laminated sheet dueto aging while the case is stored for a long time. It was found throughthe examination of causes of delamination that the adhesive layer of asolvent type adhesive used for dry lamination dissolves in anelectrolyte, i.e., a component of a polymer battery, in a long timebecause the electrolyte is an organic carbonate solvent. The electrolytepermeates the resin layer of the case gradually, reaches the interfacebetween the resin layer and the adhesive layer and, eventually, thelaminated sheet delaminates along the adhesive layer.

The inventors of the present invention found that the delamination of alaminated sheet due to the agency of the electrolyte can be prevented byprocessing a surface of an inner layer to be bonded to a metal foil by aplasma arc treatment, and a battery case forming laminated sheet highlyresistant to the dissolving action of the electrolyte can be produced byusing either a dry lamination method or a heat lamination if a surfaceof an inner layer having a surface to be bonded to a metal foil isfinished by a plasma arc treatment.

A surface of an inner layer to be bonded to a metal foil is finished bya plasma arc treatment. Suppose that a laminated sheet 10 has aconstruction: first base film layer 1 a (PET)/LMD 125 (drylamination)/aluminum foil layer 2/third base film layer 1 c(ON)/heat-adhesive resin layer 3 (acid-denatured polyolefin resin layerformed by extrusion coating) as shown in FIG. 74. Then, a surface of thethird base layer 1 c, i.e., the ON film layer, on the side of thealuminum foil layer 2 is finished by a plasma arc treatment to form aplasma arc processed layer 126.

When a laminated sheet 10 has a construction: first base film layer 1 a(PET)/LMD 125/aluminum foil layer 2/heat-adhesive resin sheet 127 (heatlamination)/third base film layer 1 c (ON)/LMD 125/additional third basefilm layer 1 d (EVOH)/heat-adhesive resin layer 3 (acid-denaturedpolyolefin resin layer formed by extrusion coating) as shown in FIG. 75,a surface of the heat-adhesive sheet 127 on the side of the aluminumfoil layer 2 is finished by a plasma arc treatment to form a plasma arcprocessed layer 126. Each of the laminated sheets shown in FIGS. 74 and75 has an outer laminated structure 122, an inner laminated structureand the heat-adhesive resin layer 3.

When processing a film by the plasma arc treatment, the film is placedin a chamber, desirably, the chamber is evacuated in a vacuum, a sourcegas, such as a functional group containing gas obtained by passing arare gas through a solution containing functional groups or a mixed gasprepared by mixing a gas containing functional groups and a rare gas, issupplied into the chamber, and a plasma is generated in the chamber by aplasma generator to treat the surface of the film with the plasma.

The rare gas may be Ar, He, Kr, Xe or Rn. Preferably, Ar is used. Thegas to be mixed with the rare gas or the solution through which the raregas is passed may be an acid, a ketone, an alcohol, hydrogen fluoride,carbon fluoride, silicon fluoride, nitrogen fluoride, a hydrocarbon, anaromatic compound, diisocyanate, an acrylate monomer, water vapor,nitrogen, hydrogen, a halogen or a combination of some of thosesubstances.

A film may be treated by an atmospheric pressure glow discharge plasmaarc treatment while the film is moved continuously instead of by theplasma arc treatment using a vacuum chamber.

According to the present invention, it is desirable to process thesurface of the film continuously by an atmospheric pressure glowdischarge plasma arc treatment method capable of efficiently processingthe film.

When processing a film by plasma arc treatment, the film is placedbetween first and second electrodes in a vessel, a source gas issupplied into the vessel, a radio frequency voltage is applied acrossthe first and the second electrode to create a glow discharge regionbetween the first and the second electrode, and the film is movedthrough the glow discharge region for continuous plasma arc treatment.

The laminated sheet 10 did not delaminate when a battery packet formedby using a battery case formed by processing the laminated sheet 10obtained by bonding the inner laminated structure 123 having the plasmaarc processed layer 126 to the metal foil layer 2 of the outer laminatedstructure 122 was subjected to a long-term storage life test undersevere test conditions.

The laminated sheet in accordance with the present invention ischaracterized by the plasma arc processed layer of the inner laminatedstructure 123 to be bonded to the metal foil layer 2. Other surfaces ofthe component layers of the laminated sheet need not necessarily befinished by plasma arc treatment.

For example, a surface of the first base film layer 1 a to be bonded tothe metal foil layer 2 need not be finished by plasma arc treatmentbecause, although the electrolyte of the battery penetrates theheat-adhesive resin layer 3 and the third base film layer 1 c, reachesthe surface of the metal foil layer 2, and dissolves the adhesive layerto cause delamination, the electrolyte is unable to permeate the metalfoil layer. It was proved that the third base film layer 1 c and theheat-adhesive resin layer 3 are not separated from each other even ifthe respective surfaces of the third base film layer 1 c and theheat-adhesive resin layer 3 to be joined together are not finished byplasma arc treatment, which is considered that the third base film layer1 c and the heat-adhesive resin layer 3 are not separated, anddelamination occurs in the interface between the metal foil layer andthe layer bonded to the metal foil layer because the electrolyte passesthrough and does not accumulate in the adhesive layer bonding togetherthe third base film layer 1 c and the heat-adhesive resin layer 3,neither dissolves nor erodes the adhesive layer, and dissolves theadhesive layer bonding the layer to the metal foil layer to causedelamination.

EXAMPLES

Examples in accordance with the present invention will be describedbelow. The present invention is not limited in its practical applicationto the examples which will be described below.

Batteries 50 a using a lithium ion polymer as a polymer electrolyte, anda carbon member were fabricated. Tabs 59 and 60 were connected to endparts of collector electrodes 57 and 58, respectively. Free end parts ofthe tabs 59 and 60 were extended outside from a case 51. The tabs 59 and60 were made of copper (positive terminal) and aluminum (negativeterminal), respectively. The batteries 50 a were sealed in cases formedby using the following laminated sheets to form battery packets, and thebattery packets were subjected to performance tests.

Example 1

PET (12 μm thick)/LMD/AL (15 μm thick)/P·T ON (15 μm thick)/HS (50 μmthick)

PET: Biaxially oriented polyester resin film

LMD: Two-component polyurethane adhesive layer formed by dry lamination

P·T: Plasma arc treatment

ON: Biaxially oriented nylon resin film

HS: Heat-adhesive layer of an acid-denatured polyolefin resin^(*1)formed by extrusion coating

*1: ADOMA commercially available from Mitsui Sekiyu Kagaku Kogyo K.K.

Example 2

PET (12 μm thick)/LMD/AL (15 μm thick)/LMD/PT ADF (40 μm thick)/ON (15μm thick)/HS (50 μm thick)

ADF: Heat-adhesive sheet VE300 (commercially available from Tosero K.K.)

The AL and the ON were bonded together by heat lamination using theheat-adhesive sheet, and the surface of the heat-adhesive sheetcontiguous with the AL were finished by plasma arc treatment. Example 2is the same in other respects as Example 1.

Comparative Example 1

PET (12 μm thick)/LMD/AL (15 μm thick)/LMD/ON (15 μm thick)/HS (50 μmthick)

Comparative example 1 is the same as Example 1, except that the ON ofComparative example 1 does not have any surface finished by plasma arctreatment.

Comparative Example 2

PET (12 μm thick)/LMD/AL (15 μm thick)/LMD/ADF (40 μm thick)/LMD/ON (15μm thick)/HS (50 μm thick)

Comparative example 2 is the same as Example 2, except that the ADF ofComparative example 2 does not have any surface finished by plasma arctreatment

Storage Life Test

Ten sample battery packets fabricated by using the laminated sheet ofeach of Examples 1 and 2, and Comparative examples 1 and 2 were storedin a thermohygrostat conditioned at 40° C. and 90% RH for six months,and then the performance of the sample battery packets was tested.

Results

Example 1: No performance deterioration occurred in all the samples.

Example 2: No performance deterioration occurred in all the samples.

Comparative example 1: Delamination occurred in all the samples.

Comparative example 2: Delamination occurred in the three samples out often.

When it is desired to print letters and pictures on the surfaces of thelaminated sheets 10 shown in FIGS. 74 and 75, the letters and thepictures are printed on the inner surface of the first base film layer,i.e., the outermost layer, to be bonded to the surface of the adjacentlayer, for second-surface decoration, and then the first base film layeris laminated to the adjacent layer. The thus printed letters andpictures will not be damaged even if the surface of the battery caseforming sheet is abraded.

As is apparent form the foregoing description, the present inventionprovides lightweight, thin, flexible, battery case forming sheetsexcellent in various kinds of mechanical strength, heat-resistance,impermeability to moisture and gases, heat-sealability andprocessability, and capable of being efficiently produced. The plasmaarc treatment of the surface of the layer to be bonded to the metal foilprevents the delamination of the laminated sheet forming the case of thebattery packet which occurs when the battery packet is stored for a longtime.

The use of the adhesive resin layer and the heat-adhesive resin layerformed of acid-denatured polyolefin resins having a meting point of 100°C. prevents the unsealing of the sealed parts of the battery case andthe resultant leakage of the electrolyte even if the battery packet isstored in a high-temperature environment.

Twentieth Embodiment

A twentieth embodiment of the present invention will be described withreference to FIGS. 76 and 77.

A conventional laminated sheet uses a nylon film as a third base filmlayer 1 c because the nylon film has high piecing strength resistant tothe piercing actions of the projection of the component members of abattery and high adhesiveness to an acid-denatured polyolefin resinforming a heat-adhesive layer, does not become thin when heat andpressure is applied thereto, and is capable of preventing a metal foillayer included in the laminated sheet coming into contact with terminalswhen heat-sealing an open end part of a battery case formed byprocessing the laminated sheet due to the reduction of the thickness ofthe heat-adhesive resin layer caused by heat and pressure applied to theopen end part of the battery case for heat-sealing.

Referring to FIGS. 76 and 77, a laminated sheet 122 has an outerlaminated structure 122, an inner laminated structure 123, and aheat-adhesive resin layer 3.

When a battery packet fabricated by forming a battery case by processingthe laminated sheet having such a construction, and sealing a battery inthe battery case is stored for a long time in an environment conditionedat a constant temperature and a constant humidity, it is possible thatmoisture permeates the case.

It was found through the close examination of possible causes ofpermeation that moisture permeates the nylon film serving as a thirdbase film layer 1 c through the end surface of a battery case 51, andpenetrates the heat-adhesive resin layer 3 in the battery case 51 asindicated by the arrows in FIG. 77.

The conventional laminated sheet uses a third base film layer 1 c of anormal chain aliphatic polyamide resin, such as nylon 6 or nylon 66.

A normal chain aliphatic polyamide resin film is hygroscopic. A batterycase forming sheet 10 may employ a film of a material having a lowhygroscopic property, such as an oriented polyester resin film. Alaminated sheet in accordance with the present invention employs a nylonfilm which can be bonded to the heat-adhesive resin layer by stableadhesive strength. The inventors of the present invention found thataromatic polyamide resins have low hygroscopic property and meetsconditions requisite for the third base film layer 1 c.

However, a film of an aromatic polyamide resin is stiff and is subjectto stress cracking. It was found that a blend of an aromatic polyamideresin and a normal chain aliphatic polyamide resin forms a stable layer.

EXAMPLES

Examples of the present invention will be described.

Batteries using a lithium ion polymer as a polymer electrolyte, and acarbon member were fabricated. Tabs 59 and 60 were connected to endparts of collector electrodes 57 and 58, respectively. Free end parts ofthe tabs 59 and 60 were extended outside from a case 51. The tabs 59 and60 were made of copper (positive terminal) and aluminum (negativeterminal), respectively.

Example 1

PET (12 μm thick)/LMD/AL (15 μm thick)/ADF (40 μm thick)/ON-A (15 μmthick)/HS (50 μm thick)

PET: Biaxially oriented polyester resin film

LMD: Two-component polyurethane adhesive layer formed by dry lamination

AL: Aluminum foil

ADF: Acid-denatured polyolefin resin film formed by heat lamination

ON-A: Biaxially oriented aromatic nylon resin film (NOBAMIDDO X21,commercially available from Mitsubishi Enginiyaringu Prastikku K.K.)

HS: Heat-adhesive resin layer of an acid-denatured polyolefin resinformed by extrusion coating

Example 2

PET (12 μm thick)/LMD/AL (15 μm thick)/ADF (40 μm thick)/ON-B (15 μmthick)/HS (50 μm thick)

ON-B: Biaxially oriented nylon film of a blend of 100 parts by weightaromatic nylon resin and 10 parts by weight aliphatic nylon resin

The laminated sheet in Example 2 employs the NO-B as its third base filmlayer and is the same in other respects as the laminated sheet inExample 1.

Comparative Example 1

PET (12 μm thick)/LMD/AL (15 μm thick)/ADF (40 μm thick)/ON-C (15 μmthick)/HS (50 μm thick)

ON-B: Biaxially oriented aliphatic nylon resin film

The laminated sheet in Comparative example 1 is the same as thelaminated sheet in Example 1, except that Comparative example 1 employsthe ON-C as its third base film layer.

Example 2 is the same as Example 1, except that Example 2 employs a filmof nylon 6 as its third base film layer.

Storage Life Test

Ten sample battery packets fabricated by using the laminated sheet ofeach of Examples 1 and 2, and Comparative example 1 were stored in athermohygrostat conditioned at 40° C. and 90% RH for three months, andthen the performance of the sample battery packets was tested.

Results

No performance deterioration occurred in all the samples in Examples 1and 2. Performance deterioration occurred in the three samples out often in Comparative example 1.

Example 2: No performance deterioration occurred in all the samples.

When the third base film layer is formed of the film of the aromaticnylon resin or the film of the blend of the aromatic nylon resin and thealiphatic nylon resin, the battery case forming laminated sheet iscapable of forming a case which does not permit the permeation ofmoisture through the end surface thereof.

When it is desired to print letters and pictures on the surfaces of thebattery case forming laminated sheets 10 shown in FIG. 76, the lettersand the pictures are printed on the inner surface of the first base filmlayer 1 a, i.e., the outermost layer, to be bonded to the surface of theadjacent layer, of the outer laminated structure 122 for second-surfacedecoration, and then the first base film layer 1 a is laminated to theadjacent layer. The thus printed letters and pictures will not bedamaged even if the surface of the battery case forming sheet isabraded.

As is apparent form the foregoing description, the battery case forminglaminated sheet in accordance with the present invention comprises atleast four laminated layers, namely, the first base film layer, themetal foil layer, the second base film layer and the heat-adhesive resinlayer, employs the film of the aromatic or aliphatic nylon resin as thesecond base film layer, is lightweight, thin, flexible, excellent invarious kinds of mechanical strength, heat-resistance, impermeability tomoisture and gases and capable of preventing the penetration of moisturethrough the battery case even if the battery packet using the batterycase is stored for a long time.

Twenty-first Embodiment

A twenty-first embodiment of the present invention will be describedwith reference to FIG. 78.

FIGS. 78(a), 78(b), 78(c) and 78(d) show laminated sheets 10. In thelaminated sheet 10, a metal foil layer 2 is bonded to an inner laminatedstructure 123 with a heat-adhesive resin layer 127 by a heat laminationmethod.

Example 1

The laminated sheet 10 shown in FIG. 78(a) has the followingconstruction.

PET (12 μm thick)/LMD/AL (12 μm thick)/ADF (50 μm thick)/ON (15 μmthick)/HS (50 μm thick)

In this construction, PET represents a biaxially oriented polyesterresin film (first base film layer 1 a), LMD represents an adhesive layerformed by dry lamination, AL represents an aluminum foil (metal foillayer 2), ADF represents an adhesive layer of VE300® commerciallyavailable from Tosero K.K. (heat-adhesive resin sheet 127), ONrepresents a biaxially oriented nylon film (ENBUREMU commerciallyavailable from Yunichika K.K.) (third base film layer 1 c) and HSrepresents a heat-adhesive layer of ADOMA commercially available fromMitsui Sekiyu Kagaku Kogyo K.K.) (heat-adhesive resin layer 4).

Conditions for heat lamination: A high-frequency welding method wasused. The ADF was sandwiched between the Al of a laminated structure ofPET (12 μm thick)/LMD/AL (12 μm thick), and the ON to form a layeredstructure, pressure was applied to the layered structure and a currentwas induced in the layered structure by a high-frequency power of 19KHz.

Example 2

The laminated sheet 10 shown in FIG. 78(b) has the followingconstruction.

PET (12 μm thick)/LMD/AL (12 μm thick)/ADF (50 μm thick)/ON (15 μmthick)/LMD/EVOH (20 μm thick)/LMD/HS (40 μm thick)

In this construction, EVOH represents a film of EVARU® commerciallyavailable from Kuraray Co., Ltd. (additional third base film layer 1 d).

Conditions for heat lamination: A thermocompression bonding method wasused. The ADF was sandwiched between the Al of a laminated structure ofPET (12 μm thick)/LMD/AL (12 μm thick), and the ON to form a layeredstructure, and pressure and heat of 160° C. were applied to the layeredstructure for 1 sec.

Comparative Example 1

The laminated sheet 10 shown in FIG. 78(c) has the followingconstruction.

PET (12 μm thick)/LMD/AL (12 μm thick)/SL (15 μm thick)/ON (15 μmthick)/HS (40 μm thick)

In this construction, SL represents an adhesive resin layer 128 forsandwich lamination. The SL, i.e., the adhesive resin layer, wassandwiched between the Al of a laminated structure of PET (12 μmthick)/LMD/AL (12 μm thick), and the ON to form a layered structure tobond together the AL and the ON by sandwich lamination.

Comparative Example 2

The laminated sheet 10 shown in FIG. 78(d) has the followingconstruction.

PET (12 μm thick)/LMD/AL (12 μm thick)/LMD/ON (15 μm thick)/LMD/EVOH (20μm thick)/HS (40 μm thick)

Conditions for lamination: The Al of a laminated structure of PET (12 μmthick)/LMD/AL (12 μm thick), and the ON were bonded together by drylamination using a two-component polyurethane adhesive.

Results

Cases were fabricated by using those laminated sheets, batteries usingan electrolyte of an organic carbonate solvent were sealed in thosecases, respectively, to form sample battery packets, and the samplebattery packets were subjected to a storage life test.

Storage life test: The sample battery packets were stored in athermohygrostat conditioned at 40° C. and 90% RH for three months, andthen the cases of the sample battery packets were examined to seewhether or not the separation of the metal foil layer and the innerlayer bonded to the former occurred in the laminated sheets forming thecases. The results of examination are expressed by the ratio: (Thenumber of cases in which the separation occurred)/(The number of samples(ten samples))

Example 1: 0/10

Example 2: 0/10

Comparative example 1: 10/10

Comparative example 2: 2/10

The foregoing constructions in accordance with the present inventionprevents the separation of the metal foil layer 2 and the innerlaminated structure 123 attributable to the agency of the electrolyte.The first base film layer 1 c and the third base film layer 1 c, or thefirst base film layer 1 c, the third base film layer 1 c and theadditional third base film layer 1 d provide the laminated sheet withvarious kinds of mechanical strength and resistance. Since the metalfoil layer 2 is sandwiched between the first base film layer 1 a and thethird base film layer 1 c, and the additional third base film layer 1 dis bonded to the third base film layer 1 c, the laminated sheet has ahigh piercing strength particularly against piecing from the inner side,the metal foil layer is protected, and hence the battery case forminglaminated sheet has a stable barrier property.

When it is desired to print letters and pictures on the surface of thebattery case forming laminated sheet, the letters and the pictures areprinted on the inner surface of the first base film layer 1 a, i.e., theoutermost layer, to be bonded to the surface of the adjacent layer forsecond-surface decoration, and then the first base film layer 1 a islaminated to the adjacent layer. The thus printed letters and pictureswill not be damaged even if the surface of the battery case formingsheet is abraded.

What is claimed is:
 1. An assembly comprising (1) a battery case forminglaminated sheet for containing component elements of a battery, and (2)tabs for connection to a battery extending outside from a battery casetherein, said battery case forming laminated sheet comprising: a firstbase film layer; a heat-adhesive layer having a thickness of 10 to 100μm comprising a polyolefin resin layer and an acid-denatured polyolefinresin layer having a thickness of 1 to 50 μm; and a metal foil layersandwiched between said first base film layer and said heat-adhesivelayer.
 2. The assembly according to claim 1, wherein said first basefilm layer is a biaxially oriented polyethylene terephthalate film or abiaxially oriented nylon film.
 3. The assembly according to claim 1,wherein said acid-denatured polyolefin resin has an acid content in therange of 0.01 to 10% by weight.
 4. The assembly according to claim 3,wherein said first base film layer is a biaxially oriented polyethyleneterephthalate or a biaxially oriented nylon film.
 5. The assemblyaccording to claim 1, wherein the metal foil layer has a size smallerthan those of the other layers, and an edge of the metal foil layer isnot exposed at least in one end of the battery case forming laminatedsheet.